FF XV in a vacuum is a good game. The battle system is fun (outside of the dumbass magic system as stated before). The world is amazing to look at (what there is of it) and the overall gameplay systems themselves are very well put together. However it is blatant that they basically got 2 of about 10 planned zones done, and when they realized that there was no way to finish the other 8 they tried to cram EVERYTHING into those 2 zones. Then, they took the story parts they absolutely couldn't and just slapped together a back drop for them to play out in and called it a day. The story is absolute shit from beginning to end. It is absolutely not set up well, nor is anything explained, nor is there any reason to care because no one outside the bros is even covered. The biggest problem is, the bulk of the story really is about everything outside of the bros' journey which is all you are really following. So it's like when bad guy attacks water city, you could give half a fuck because who is this guy?
Also as a final fantasy game it absolutely does not feel like a final fantasy... at all. There are a few stylistic throwbacks like some of the monsters are classic FF monsters. Some of the menus have graphics with the old school 2d sprites stylized like old FF. But it feels closer to something like GTA/Saints Row with some token dragons thrown in on the side. Again in a vacuum and as its own game, that would have been fine, but it goes against it with a final fantasy in the title. I agree with the above that anything past XI hasn't really felt all that "Final Fantasy" to me. In fact, while I loved X, I'd argue since IX. X was the first real departure from the game with the sphere grid, and the removal of the over world. That was right around when Sakaguchi left, so it always made sense to me. Then XII was different in many ways as well, but still much closer than anything that's been released since then. Sadly when the Guch left, it seems so did the soul of that franchise and everyone has been trying too hard to put their own stamp on it thus stripping the game of it's core identity that tied all the games before together.