-A party of interesting characters. I REALLY don't want it to be a 1-character thing. This to me is a key piece of Final Fantasy.

-Huge and varied, non-linear world. It doesn't need to be full Skyrim-style open-world. But just something fairly open where you need to explore a lot and can backtrack to previous locations. None of that FFXV "and now the rest of the world becomes off-limits, unless you want to time-travel into the past" silliness. Something like the world of FF12 would be good. Constrained and segmented but open and non-linear.

-Mini-games! They've really slacked on this in recent times. The thing I loved in the PS1 era is how they all had these huge mini-games that would almost span the length of the whole game, and have important benefits for the main game too. So Chocobo breeding/racing in FF7, card game in FF8, Hot n' Cold in FF9. We need something like this to come back. They haven't done anything like this really since Blitzball in FFX. Battle square/ hunts type thing doesn't count. It has to be something other than just more battles.

-A love story! It's been a while since they did a good romance. FF8, FF9 and FF10 all had really love stories, and then they just did nothing for several decades. Nothing in XII, nothing in XIII, and then an almost trolling provocation of a non-romance in XV.

-No time travel, no alternate dimensions, no fighting against abstract concepts. The number of times where injecting metaphysics into a story actually improves it can be counted on one hand.