I mean, I'm going to have to disagree.
I'm over the moon that characters like Banjo, Steve, etc are here, but if the game isn't fun to play, then even though they're here, that means little if playing online feels like a chore. There's nowhere near enough single-player content in the game to justify just playing solo all the time, meaning that Online is supposed to be a key function of Ultimate... and it's bad, real bad, like, abysmally bad. I can only play against CPUs soo much before I get bored and want something new, and since Ultimate seriously lacks Singleplayer content, Online is supposed to be what makes up for it, but, it falls flat.
I agree that the Switch's online infrastructure needs work, but I'd still take rollback over FP3. I'd rather try to fix a turd than polish it. I love Ultimate, I love its roster, but if it's a literal chore to play it, then no amount of bonus content is going to fix that. Shiny new things are only going to keep my attention for soo long before I realize "Oh wait, this sucks to play." Stacking new stuff on top of something with flaws isn't fixing an issue, it's only covering it up and trying to divert attention away from it.
Smash isn't just an "oogle the roster" simulator, it's a game, meant to be played, and if playing online in 2021 is something that's not working well, something isn't right.