Look at this way: cinema is a young medium. It’s barely over one hundred years old, and cinema with sound is less than eighty. Many of the film classics we know are developmental works, famous because they were the first to utilise a particular technique. The technical capabilities of cinema continue to expand, and as they do so the artistic boundaries expand concurrently. Filmmakers are still exploring the limits of the medium, which is part of what makes filmgoing so fun. This means that more recent films are at least potentially able to draw on a richer heritage of filmmaking experience. Think of it like a language: as the language matures, the vocabulary available to its speakers increases.
Which is not to say that any older film is inferior to a more recent film: few films (old or new) make use of the full possibilities the medium presents, and the form was mature enough by about the forties that good filmmakers could achieve results that still look exceptional today. (Citizen Kane, for example, is still astonishing as both a technical and artistic achievement). Yet if you believe that something was added to cinema by the French New Wave, or the “New Hollywood” of the seventies, or the Hong Kong Cinema of the eighties and nineties, or any of the other important filmmaking movements of the last fifty years, then don’t you have to believe that the artistic possibilities open to a filmmaker today are richer?
I think it's a good argument, and a true one in some cases. I don't quite see eye-to-eye with it, as you might expect from someone who started a blog to write mostly about old stuff and who is constantly arguing for the validity of older works, older styles. While I think new works can be richer for the range of options available to them, I don't think they always are.
The easiest example to use here is not movies but music, because its new techniques are based on almost scientific principles (and therefore it's sort of possible to quantify innovations in music). As the history of Western music progresses, you can see that pattern of artistic development, at least broadly. Orchestras get bigger, there are more instruments and more sounds, harmonies get more complicated, and composers become open to more influences from around the world. There's no question that the history of music has benefited from all this.
But does that mean that the language of music matured or even got richer at any particular time? It depends on what you mean by richer. Sometimes Western music would become more advanced in one area, like harmony, while getting simpler and squarer in another area, like rhythm. Early music has a spikier sound than Romantic music that sometimes makes it sound more "advanced" in certain respects. Pop music is the same way, sometimes becoming simpler than what came before it and limiting, rather than expanding, the range of choices available to it. It's not about getting better or worse -- but while there's always a style that can be identified as contemporary and current, it's not always possible to say that it embraces all the historical possibilities of the form, or that it builds upon its predecessors to be more technically advanced in every area.
The same applies to movies. There are a lot of choices open to filmmakers thanks to the longer history of the medium -- in theory. In practice, most movies at a given time tend to share a common basic grammar, which means that certain choices will usually be made and others not made, almost instinctively. As I've said in the past, the two-shot, with two characters interacting and communicating in the same frame, was one of the basic units of film from the silent era and for decades after. Now putting two characters in the frame together without cutting between them is almost a special effect; it's still done, but it cuts against modern filmmaking instinct.
What I guess I'm saying is that, in a medium with any current popularity, the creator makes a lot of stylistic choices, but others are almost made for him or her, unconsciously. That's why the music or literature of a particular period tends to share certain stylistic traits in common, even as the great artists add their own voice to the prevailing style. Same with movies. Like the structure and sound of a popular song, the style of a movie is defined partly by the filmmaker but partly by the time period.
Which means that the range of choices open to the filmmaker is never quite as broad as it might seem, no matter how much history comes before it. A Coen Bros. movie is a Coen Bros. movie, but it's also a '80s or '90s or '00s or '10s movie, and if you break it down beat by beat and shot by shot you'll see a lot of choices that are similar to other movies of the time, just as even Citizen Kane has plenty of moments that mark it as an RKO movie from 1941.
And this is as it should be, because a) art has a large instinctive component, and instinct is shaped by the time one lives in, and b) an artist who actually wants to put his or her work before the public usually has to create something the public will recognize as contemporary. Most movies exclude certain choices that would be seen as belonging to the past. Unless it's a crazy stunt like The Good German, and even that has a ton of contemporary visual style in it. But anyway, many things an older film, even a recent older film might have done, can't really be done today. They belong to another time when a combination of instinct and intellect made those particular techniques possible.
Which is why I don't think we really build on the past to a great extent. We do sometimes, but so much of what artists do is set in stone by the prevailing style that a look back to the past seems instantly anachronistic -- like Mozart dipping into the Baroque style and quoting the "Hallelujah Chorus" in his Great Mass in C minor, or Altman in The Player parodying (or paying homage to, but mostly parodying, I think) the heavy-footed camera moves of Touch of Evil.
Artistic boundaries expand, but they also contract, and perhaps with the exception of the occasional visionary, particularly the Charles Ives or Emily Dickinson who doesn't feel a need to put his or her work in front of a broad public, any artist is a prisoner of his or her era. That's fine, but it means the choices aren't really broader except in an almost mechanical sense: quicker and smoother camera moves, less obvious rear projection. And even the mechanical improvements arguably have their disadvantages -- or at least you can't say that an earlier film, which found a perfect way to use the equipment available, would have done better if it had had the later equipment. It would have done the shot differently, not always better.
It means, as I see it, that we can't usually look at an older work and say that a later work is more advanced, even in raw technical terms. For it to be more advanced, the later work would have to do the same thing the earlier one does, only better or more complex. And the later work can never do that, just by virtue of belonging to a different time. The early work is not "better" in technical terms (unless we're comparing a great work to a not-great one), but it is precious because it can never truly be surpassed. The game has changed.