It's hard to have fun with a win button, casual perspective or not, so no I'm not missing the point. They're poorly designed, in and out. Poorly implemented to boot.
I'm 100% okay with items (save a few) yet I'd never want to play with them outside of friendly settings on nights where I'm drunk with friends, which is rare. I still like items, despite never using them and understanding how they hurt competitive play. Final smashes, on the other hand, I just hate. They're outright bad and have been since Brawl.
At least, in theory, if a busted item falls to the stage anyone in the match can pick it up and use it. Final smashes are poorly balanced win buttons in many instances where one character will have a total joke of one, then their opponent have one that can kill at 0%. Casual, competitive, intoxicated.. however you play the game, they're objectively flawed.
They should've NEVER been based on Smash Ball items and always should've come out of a built-up meter overtime like in Ult. They could have a stronger version in Smash Balls for item games, but they should've never been the original / primary means of obtaining them. Going forward, they should've been balanced FAR better. I understand you can't make it all equal, but it's inexcusable to have some characters have a FS that's basically not even worth using while other ones have a literal 0-death win button. Poorly designed AND poorly implemented like I said.
I WISH, they weren't. As said above, I'm fine with the idea of super moves in fighters even if I personally don't like them, but the way Smash has done it is just.. bad.