The obvious implication at this point is that Feige and crew a) resent Perlmutter for trying to push the Inhumans on them and shunted him out of the process so they don't have to bother with his nonsense, b) simply weren't interested in making an Inhumans movie, or c) couldn't figure out a way to actually make an Inhumans movie work, which speaks volumes of the material considering they still haven't made a less-than-good film yet and even THEY can't figure out how to make it work, at least without chucking the more "problematic" parts of the Inhumans stuff, which basically comprises of a good chunk of the core in the first place.

If Feige and co either weren't interested or couldn't make Inhumans work and palatable without changing the whole setup considerably, that's kind of a red flag.