Final Fantasy XIII Wasn't the Beginning of the End. It was Final Fantasy X
People like to point to Final Fantasy 13 as the beginning of the end for good Final Fantasy games with moving away from expansive worlds into a hallway sim with more and more complex battles systems but the reality is that X did it first and arguably just as bad. The first 4/5 of the story you're met with almost zero exploration as you traverse a glorified hallway with the seeming saving grace that you can sometimes go backwards in this hallway until you hit one specific area where the game... Kind of opens up? Before thrusting you back into more hallways until the end.
FFX is widely acclaimed but it's 100% the reason FF games went the way they did. Thank fuck for XII giving one last good entry though.