I've got a good spoiler to throw into the discussion about ffxvi supposedly cutting many series traditions: what's the functional distinction between the eikon forms and a conventional party member?
in both cases, it's a new set of mechanics that a player can optionally incorporate into their setup. one is just in the wrapper of a character, while the other is contextualized as a broadening of the single character's abilities
going a little further with this argument, if someone were to say that the wrapper creates a big difference there, then I'd ask what the distinction is between a party member and a character is. several characters in xvi are, going by screen time and contribution to the story, measurably more of characters than some party members in previous mainline FF games (I could point out at least one party member in each game who have almost no story presence)
this is a series that hasn't had much to set itself apart in the sphere of turn based RPGs and is often fairly shallow compared to other RPGs in that respect. I think a lot of the stuff older fans hold onto is window dressing at best, with xvi making massive improvements in the areas that previous games have routinely flopped on: combat depth, character development, and narrative cohesion