The problem with ulti is the lack of single player content, and crappy online mode.
The main gameplay is the best it's ever been yes, but it came at the cost of the single player content which made the entire game stale. No BTP, BTT, Melee events mode, Melee Adventure mode, Boss rush, a non gimped all stars mode, and Smash run, all gone.
>B-B-BUT WHO CARES ABOUT THAT SHIT IN A FIGHTING GAME
playing the same main gameplay as the only form of any enjoyment for a game like smash is going to get stale. This is something Brawl addressed well, despite the shit gameplay.
SwSh, on the other hand is looking to have meh core gameplay, and even worse content. Oh and a crappy online as well potentially.