Look, I know why Gilbert and Sullivan are so popular with schools and societies all throughout the Anglosphere (tm). Because G&S wrote their works for a stock company, there are no "star" parts; instead there are a lot of parts that get roughly equal time and equal opportunities to shine. There's a fair balance between male and female roles, and lots of work for the chorus. Each act requires only one set. The music is fun and relatively easy to sing. There are few complicated scenic or special effects beyond the occasional requirement for Peers to sprout wings. They are fun and easy to put on.
But the insane overexposure of these relatively few works has created the familiarity that breeds contempt: the cliches of G&S, and of G&S performance, are so familiar now that it would be hard to find an audience for a fresh musical or dramatic approach to any of these works. If G&S performance was once defined by the musty traditions of the D'Oyly Carte company, it's now defined by the broad mugging and musical compromises of the typical semi-pro performance. But how can you do a really well-sung, well-staged version of H.M.S. Pinafore when everybody has already seen it, or even done it, a million times? The only answer is to let these works sit on the shelf for a while, so they can be "rediscovered" later and re-evaluated for the excellent works they are.
The question then becomes, however: what would a re-thought, well-staged version of a G&S operetta be like? It's not like people haven't tried to breathe some new life into G&S. Before Gilbert's copyright expired in 1961, G&S performances were controlled by the D'Oyly Carte company, which used mechanical, predictable blocking and hoary old bits of schtick that had been around for decades (but probably weren't around in Gilbert's time). Flanders and Swann hilariously satirized this in their song "In the D'Oyly Cart":
Dear little town of Nanki-Poo
(Smile, turn, pace to the right),
Canst thou believe my heart is true?
(Terrible house tonight!)
One that with tender passion fired
(Turn, pace, hand over heart),
Woe to the day that we were hired
By D'Oyly Carte!
Why is it so admired,
This business first inspired
By former artists long retired
From D'Oyly Carte?
With the expiry of the copyright, various directors and companies jumped in and started trying to find a fresh spin on these works. Some of the more successful attempts were Tyrone Guthrie's productions of Pinafore and Pirates of Penzance at the Stratford Festival in Ontario and City Center in New York, the Sadler's Wells (now English National Opera) productions of Iolanthe and The Mikado (the latter, with Clive Revill as Ko-Ko, produced an excellent recording, and EMI's series of recordings with prominent opera and oratorio singers. And later, of course, there was Joseph Papp's hit production of Pirates with Kevin Kline as the Pirate King and Linda Ronstadt as Mabel. The D'Oyly Carte company, sticking as it did to the old mechanical stage business, faded into irrelevance and eventually folded; it re-constituted again in the '90s and has since more or less folded again.
Most of the "new look" G&S productions mostly consisted of clearing away all the old gags and business, or enforcing higher vocal standards than the D'Oyly Carte used to tolerate. That can still be done today: take out all the familiar schtick from semi-pro productions, and make sure the singers and orchestra are up to snuff. The problem was, and still is, that once a director has gotten through taking out all the bad habits that have affixed themselves to G&S, there's not a lot he can add to make the works fresh and new. G&S operas are essentially director-proof. There is no depth to the characters; any stage action you can add during a song just detracts from the song (which is why I think any G&S director should keep movement during a song to a minimum and not, repeat not, introduce physical gags in the middle of a song); all the social commentary is right there on the surface. Once you've done the now-traditional rewriting of patter songs to add lame topical references, you've just about done everything you can do.
The best bet with G&S, then, is at the musical end: cast really good singers, do lots of musical rehearsal, emphasize the grace of Sullivan's music and orchestration, give the works the same amount of musical respect that is given to Offenbach and Johann Strauss. You may lose some of the fun that way, but people will discover things they hadn't known about the works -- specifically, how good, really good, the music is. The act I finale to Iolanthe is as good a finale as has ever been written, telling a lot of story in music, shifting from mood to mood and style to style with ease, a parody of grand opera that also manages to be truly operatic in scope. Taking the whole thing "straight" rather than hamming it up would help to reveal that. But ultimately, I think the future of G&S is limited by the fact that there's just not much left to discover in them: we all know the words, we all know the tunes, we all know the best lines, and there is not much left to find out about these pieces.
When it comes to G&S themselves, it's interesting that these two men, whose lives really weren't all that interesting, continue to fascinate so many, even to the point that directors take time off from making hard-hitting working-class dramas and make movies about Gilbert and Sullivan instead. I think the fascination of G&S is that they embody the mysteries and frustrations of the collaborative process. Here were two men, exceptionally gifted in their respective fields. They didn't like each other all that much, wrote together mostly because producers put them together, had very little in common in terms of artistic personality. And yet they discovered that for some ridiculous reason (to which, however, I've no desire to be disloyal), they could only produce their very best work in collaboration with each other; working apart, with more seemingly compatible collaborators, never produced the same results. Where does the magic come from? Why should two mismatched talents match up so well? These questions apply to more than just the arts -- they apply to any situation where people do good work together even though by rights they shouldn't -- and that's the fascination of the story of Gilbert and Sullivan.
Gilbert produced some excellent work on his own; the "Bab Ballads" are wonderfully gruesome comic poems, Engaged is a comedy that heavily influenced Wilde's Importance of Being Earnest, and His Excellency is almost as good a comic-opera libretto as Gilbert's work for Sullivan (unfortunately, Gilbert gave it to another composer to set, and it flopped). Sullivan's non-Gilbert efforts don't hold up as well, being too closely tied to Victorian ideas of what good serious music should be -- that academic, fussy style that creeps into some of Sullivan's operetta scores, like The Yeomen of the Guard. On the other hand, Sullivan's contributions in the operas were more consistently good; Gilbert could be wildly uneven, falling in love with bad ideas (the idea of a lozenge that turned hypocrites into whatever they pretended to be, which he finally turned into the nearly-incomprehensible The Mountebanks) and re-working his old ideas (Princess Ida's libretto is taken from Gilbert's early blank verse play based on Tennyson's The Princess, and the relative unpopularity of the work was almost entirely the fault of the leaden plot and dialogue that Gilbert had carried over from the earlier play).
Someone -- I think it was Ken Furie in High Fidelity magazine -- once said that the key to the success of G&S is that Sullivan actually believed in the humanity of Gilbert's stick-figure characters. He has a point. Gilbert didn't seem to like people very much. His poems brim with cruelty and violence; unlike the dismally boring Edward Lear, he wrote light verse not as an escape into nonsense but as a window into a nightmarish version of our own world. (See the great ballad "Etiquette", or "The Yarn of the Nancy Bell," which makes South Park look like a paragon of good taste.) His taste for cruelty carries over into the operas, in a watered-down version; his "serious" libretto for Sullivan, The Yeomen of the Guard, is an incredibly nasty piece of work where jerks get rewarded and all the nice characters either are forced to marry horrible people or wind up lonely and depressed.
As a poet and as a playwright, Gilbert was obsessed with the idea that people live their life according to stupid, pointless rules. This may have come from his unhappy years as a lawyer, or his observation of Victorian society, or both, but the plots of most of the G&S operettas revolve around stupid rules that the characters follow, and never question, even if it nearly brings them to ruin. Fredric in Pirates of Penzance believes that doing his "duty" is more important than any demands of sense, logic, or morality; Iolanthe is about the harm wrought on people's lives by the necessity to follow the law (both mortal law and fairy law); Ruddigore is about characters who live according to etiquette books and the laws governing dramatic stereotypes (if you are designated as the villain, you have to act like one, period). It's all a fascinating perspective on law, morality, and the parallels between social convention and stage convention. (To Gilbert, we are like stage characters: acting a certain way because that's our designated role, not because it makes sense.) But it doesn't make for very interesting characters, because Gilbert sees everyone as an automaton, a puppet of convention and rules. His view of human nature is best summed up by a song from The Mountebanks, sung by characters who have been transformed into clockwork figures, and sing directly to the audience:
If our action's stiff and crude,
Do not laugh, because it's rude.
If our gestures promise larks,
Do not make unkind remarks.
Clockwork figures may be found
Everywhere and all around.
Ten to one, if we but knew,
You are clockwork figures too.
And the motto of the lot,
"Put a penny in the slot!"
Sullivan, with his cheerful tunes and good-hearted sentimentality, wrote for these clockwork-figure characters as though they were three-dimensional human beings. Some of this is a problem; Sullivan almost totally neglects the dark and ironic stuff in the libretto of Yeomen, producing a lovely score but one that treats the story as if it were far less unpleasant than it actually is. But on the whole, it's effective because it leavens Gilbert's unique nastiness with heart, and the music allows for more scope in the acting (you can't act Gilbert's characters by doing much more than the kind of simple gestures that Gilbert wrote into his prompt-books; but you can give the characters some shading by your way of delivering the music). And on the rare occasion that Gilbert provides a story with a little depth -- the title character of Iolanthe seems almost real and human, even though she's a fairy -- Sullivan can be truly moving. As Conrad L. Osborne remarked, the genius of the sentimental songs in G&S is that they are both sending up sentimentality and giving in to it: "Is it funny or touching? It's both."
So if Astaire gave Rogers class, and she gave him sex, I guess you could say that Sullivan tempered Gilbert's misanthropy, and Gilbert tempered Sullivan's treacliness. Gilbert's cruelty is as much a part of Victorian culture as Sullivan's sentimentality; it's the genius of combining the two strands of Victorian culture -- the nasty and the nice -- that makes these works so special, and so good.