I like Ben Affleck as an actor and director. I'm not interested in gangs, prohibition or films set in that era. I suspect I'm not alone in that. I didn't see the Godfather movies till around a decade ago. What struck me was how much better the Sopranos was in comparison.
A lot of actors seem to want to do a niche movie as a passion project or to work with a particular director. I saw The Peacemaker with Clooney on tv the other night. He was good in it and it's not a bad little film. I watched Hail Caesar, which was comparitively regarded as superior. I thought it a load of smug, self indulgent nonsense.
Different strokes etc. However, studios must be aware the interest in period piece movies just isn't there on any sort of scale.