FFX is probably in my top 5 of JRPGs
Chrono Trigger
FF7
Persona 5
FFX
Arc The Lad
I definitely didn't love FF12, but the rot definitely starts with FF13. Though you could argue it started with FFX-2.
Nomura's increased influence on the franchise and the pushing out of creative leadership across Square. The unfortunate merger of Square and Enix, removing the biggest JRPG rivalry between the big two. All of which resulted in a lack of variety and quality among RPGs and that increased focus on FF, DQ, and KH...
Could you imagine if Square Enix had put resources towards Star Ocean, Mana, Xenogears (no Xenoblade), Chrono, Parasite Eve, Soul Blazer, Tactics, Valkyrie Profile, Vagrant Story...
Instead of making Final Fantasy into an action game, they built up Kingdom Hearts, Mana, and Star Ocean to the same level that Nintendo built up Zelda...
We're in the wrong timeline.