In the case of FF, i'd argue they didn't try to make a "Final Fantasy" game again. As much "old FF" Remake and Rebirth are, there's still the caveat that it's one game split up into three parts.
DQ team make DQ games, it works.
Persona team makes Persona games, it works. (Partially applies to SMT too here)
MonHun teams make MonHun games, it works.
Of course, there's also long running series which made a big break-out by changing the formular, see GoW and Zelda.
Though in this case i'd argue the dev teams went to think about how a change in formular might work, and went to deliver good games on this base.
So, SQEX either has the option to go back to what made FF big to begin with, or try not to half-ass things and change formula with every new game in hopes one of them works.