It's a good horror film
The first third of the film, until the elephant man is fully shown, can be watched as a decent horror film. That's because we know that the man looks horrible, but we have not yet seen him, and that creates a tension in a viewer - how shockingly horrible will he be?
I came to this board expecting to see discussions about the horror aspect of the film. But to my surprise, nobody seems to consider that aspect important. Sure, the film is more than just a horror movie. But I think the horror element should not be discarded.
In fact, I believe David Lynch willingly wanted to introduce the element of horror, at least until the man's appearance is fully revealed. That explains why he didn't show the elephant man for a long time and we finally see him along with the young woman who cries out in shock. After that moment the film turns into a melodrama and, you could say, it goes down from there.