The screen gives you a real visual of your focus, it splits your subject onto two planes unless its perfectly in focus so is very easy to get clean sharp shots and quick focus. Its a device from the old school of film cameras
Getting great results depends on all parts of the puzzel falling into place, if any one part of that fails the results will be poor. Now think of the developing of the film, I stopped shooting film due to being left at the mercy of the lab boys and the cost, for me thats a massive part of this and one that would make me look at the minor issues you are suffering comparred to the potential ones you could encounter if you switch to film.
Just my 2p's worth