I liked FFXV a lot, but it suffered from a really bad development hell and contractual deadlines, not to mention a complete change in hands in terms of directors (and therefore vision).
The issues with XV is that they tried to make a Compilation of FF7-styled universe for FFXV straight out of the gate, and while in the beginning, it was exciting... In retrospect, it's probably the one thing that ended up hurting the game the most. A lot of the story and lore in the XV universe happens in supplemental media like the Brotherhood anime and Kingsglaive. Brotherhood had backstories that should've been implemented in the game, but are barely referenced. Stuff like Prompto wanting to lose weight because he felt insecure about himself and didn't think Noctis would be friends with him because of it is a HUGE piece of Prompto's story and the fact that it's not in the game is crazy.
Or the fact that Gladio didn't even really respect Noct at first because of how lazy he was, but came around to respect him because he ended up taking the blame for Iris after she ended up getting lost.
Or even how Ignis has always been Noct's right-hand man and had to clean up after Noct's messes because of how lazy the kid was. And the only reason why Noct was so lazy and rebellious is because he just wanted to be a regular kid, he didn't want to have to deal with his dad eventually dying. Because to Noct, his dad means the world to him. So seeing his dad getting older and his health sorta declining, he ran from his responsibilities in order to cope, knowing that one day he's gonna have to take charge as an adult. He can't be a kid forever.
And that's why I like the overall world of FFXV, the entire message throughout all of the media, despite how disjointed it is -- Yeah, it's a story about repelling the darkness with light and restoring peace to the world. But at the core, it's about growing up and dealing with the cards you're dealt with. What it means to be an adult, which means doing things you don't want to do because if you don't do it, who will? And, just how important it is to have friends that really support each other through everything, because sometimes it's only your brothers who'll truly keep it 100 with you. Ardyn is what would've happened to Noctis if he didn't have any of that. Even when the world shyt on Noct, he still had people in his corner. Ardyn had absolutely nobody to steer him right, even his fiancee and brother lied on him, and then had the Astrals giving him one last fukk-you to send him completely off the deep end.
But you would never get this message if you only played FFXV, which is why I don't blame people when they say they don't like it at all. You shouldn't have to go in multiple directions to get a basic story, and the only real reason I know all of this is because I'm still invested from back when XV was Versus XIII.
Eugh I just booted up XV and bleh idk what they were thinking with that battle system

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Back when Nomura was heading it, Versus XIII/FFXV was essentially supposed to be a darker and realistic version of Kingdom Hearts. The original battle menu back in the V13 days was very KH-like, and the combat was as well. But, you could switch to different party members. When Nomura ended up getting removed from XV to finish KH3 (and eventually FF7R, but he never knew he'd be the director until later on), that's when a lot of the OG XV stuff changed. So that's why the battle system might be the way that it is. It has potential, but never really reached it. The Warp-Strike is a really cool technique, and the weapon switching mid-combo is pretty fascinating as well, but it needed more polish.
In fact, most won't realize this, but... A lot of the features in FF7R you can tell were probably intended for FFXV. Notice how FF7R has some KH-like elements, even though the combat itself doesn't play like a Kingdom Hearts game? Like the Shortcut Menu for example? Even the Main Menu for KH3 and FF7R have similar elements. I'm not saying FF7R is literally recycling Versus XIII ideas, but there probably some elements and concepts for the combat system and field exploration that ended up carrying over.