I think the reason Persona 5 has issues breaking out in the west is that it's literally anime. Final Fantasy games have been pretty anime by game standards, but it also has a historical precedent of being like that so it gets a pass and has never gone to an extreme level.
I think fantastical elements, even ones with hyper realism like XV has, is more marketable in the rest of the world than being a Japanese teenager making friends in high school getting into metaphysical battles with gods, demons, and lingering doubts about homosexuality.
While a lot of people are angry Persona games don't get the same cred and sales as FF, I think for what game and what it's about it does exceptionally well.