I'm not a fan of the emphasis on action in Final Fantasy (to me, the ATB used in FFIV-FFIX is a fundamental part of the series), and Square hasn't convinced me that they can actually make a good action game (I liked Nier Automata's combat well enough, but it was developed by Platinum, not Square). Final Fantasy XV had by far the worst gameplay in the series, in my opinion, so the similarities I see between this game and FFXV do not inspire any confidence in me.
That said, I will still have fun with Final Fantasy XVI if 1) the action combat is actually fun this time or 2) the rest of the game is so good that I don't care about the combat sucking. I wasn't a fan of the combat in FFXII, FFXIII, or FFXV, and it wouldn't have bothered me nearly as much if I'd liked those games' stories. I'm a lot more willing to put up with mediocre gameplay in an RPG if the story makes up for it, at least.
In any case, I'm going to wait for more info and until I have a chance to play the game before judging it too harshly. Maybe the game will have party members and other playable characters. It's hard to say after only seeing a four-minute trailer of an unfinished game.
It will never stop being sad that Square Enix feels that Final Fantasy needs to become an action series while ignoring that people liked Bravely Default and Dragon Quest XI for a reason. And god forbid SE glanced over at Atlus and saw how to make a turn-based system deeper and more engaging. The whole thing is so silly. When I see FFXVI acting like Devil May Cry it feels like an old man trying to be young and hip.
Seriously, Square acts surprised every single time one of their turn-based games, like Bravely Default or Octopath Traveler, sells well, and it annoys me to no end. The only reason I came to like either of the Square or Enix big franchises is their turn-based games, and I'd like to see them try and make another big budget turn-based Final Fantasy and see whether it's a success or not before they say that turn-based games will not sell. The last time they committed to a turn-based Final Fantasy (with FFX), it sold extremely well.
The argument of "let DQ be traditional and let FF evolve" makes sense to a point, but DQ fulfills a niche that is quantifiably different than say, the PS1-PS2 Final Fantasy titles, and I think the franchise and company should be strong enough to branch and support both. It's not enough to say "if you're a final fantasy fan and don't like action games, tough, go play dragon quest instead".
If the Persona and SMT games show anything, it's that turn-based games can evolve, too. Oh well. I'm basically resigned to Square never making the kind of Final Fantasy game that I want again.