As I see it, there are three major problems with the film version of A Chorus Line . Second, the filmmakers had no faith in the original vision of the play. Third, the wrong director was chosen. There are other minor problems with A Chorus Line , but these three caused the greatest difficulties. For this kind of money, you have to shoot pretty fast.
Musicals are notorious for their costs.
While A Chorus Line doesn't require elaborate sets or costumes, the time and effort required to produce really first class dance numbers weren't possible under the film's budget. I suspect that this is part of the reason that A Chorus Line rarely shows us an entire dance number. They probably couldn't afford to shoot most of them right, so only the best bits and pieces show up on the screen, with cuts to the patched-in story or reaction shots filling the gaps. Which brings us to the second problem. David O. Selznick, who was probably the most successful transcriber of good books into good films, said that, when adapting a beloved work to a film, the audience would understand if you had to leave things out, but had little tolerance for things changed and less for things added.