It's quite simple:
Zelda still has Miyamoto.
Final Fantasy hasn't had Sakaguchi for over two decades.
This is true.
But it also assumes the IP's mission statement (trailing far behind the first goal of making money) is the same for both franchises. It's clearly not.
Even in the Golden Era most Square(soft, typically) fans refer to with the Gooch at the helm, the releases were still in an anthology format, with differing worlds, bestiaries, gameplay gimmicks, etc. Let's just look at the first three games in BOTH franchises:
Zelda 1. Classic beloved game. Launched a franchise, created the series blueprint, essentially, the norm that all experimentation and risks are based on.
Final Fantasy I. Classic, beloved game. Slightly more niche and jank than Zelda 1, but all the same, basic template for the series "normal," state. Has a legacy.
Final Fantasy and Zelda II. Both took the basic gameplay and turned it on It's head. Both are, to this day and dozens of titles later, considered black sheep of their respective franchises. This is the important part. This is the divergence. Both were critically panned, and both developers had to go back to the drawing board for the third entry. Zelda took route A, and harkened back to their success before, just in a reimagined, functionally and visually superior way. This is textbook Zelda, as you'll find it has the light reboot idea several years before it become inundated in the mainstream. Think on it. LTTP is essentially Zelda I given a narrative that isn't contained entirely in the manual. OOT is basically LTTP but it's 3D now! TP is basically OOT for the Dark edgy emo gen. They saw the poor reception to "a different take," on Zelda, and course corrected by sticking to one formula, over And over, only recently breaking out of that mold.
Final Fantasy, for it's parallel part, saw the reception to FFII, and threw out the entire battle system, character growth system, and created an entire Class changing system in their light hearted four heroes of legend sequel to the game where David Bowie destroys the world and you see people, enslaved and hopeless. Then FFIV rolls around and you have fixed parties and classes and a deeper narrative, and the point is...
Final Fantasy has chosen, again and again, route B, which is to see something didn't work, and decide, instead of going back to a previous idea that worked well, they'd just go in a completely different direction next time. It's a different but equally functional answer to the same problem. But it simultaneously illustrates that it's going to appeal to different types of gamers.
Some people want reliable. Some people prefer the anthology approach, because it means that should a dev team pick a direction that the individual player thinks sucks, then by and large, they can know that the franchise hasn't been set in stone for 20 years. I dunno.
