Theatrical plays or musicals will not always translate well into filmic language, that's well known and will not change, because both media are very different by nature. To question it is to deceive yourself.
Personally I've never believed that Cats is a great musical but perhaps its success says something else but even so a film adaptation in my view just could not work. I didn't see how, especially considering the costumes but it was being made so the question now was how it was going to look.
I know there's already a ''movie'' but that's basically a recording of the play.