Capitalism might be indicating the optimum story length,
The story itself dictates the length. Hamlet needs five acts, A Zoo Story by Edward Albee, doesn't.
Obviously, studios will try and keep some times at a certain length so they can have as many screenings in a day. But, not all movies are the same length.
TV shows, because of scheduling--and yeah, commercials, are going to fit into certain slots. But, then, not all TV shows. Especially those on streaming channels or premium channels where time slots are more flexible. An episode of Jessica Jones isn't always the same length. Fargo, in it's first season, those episodes were like 75 minutes with commercials.
And as far as independent filmmaking, the scope of the story would dictate the length of the work.
but it will be interesting to see what new thing emerges from CBS trying to restrict fan films to a non-optimum story length.
For those who are willing to embrace a creative challenge, I think there could be lots of interesting creative work to come out of it. Those who are upset about limits... well, they won't make anything, I would expect. Especially, now they have a reason to not do it.
People who are creative, create.