I actually agree. I'm apparently one of the few people who actually enjoyed SSE.
I wish there was a scaled down version of SSE. No crazy expensive cutscenes, just a bunch of levels. Basically something between Melee's Adventure mode and Brawl's SSE. It would've been something more to do in the single player game besides just playing Classic mode over and over.
I wouldn't want SSE to return, but back in the Melee days I always dreamed of each character (or series, more realistically) having their own Adventure mode with enemies and locations unique to their franchise. It'd have to be shorter than Melee's adventure mode, but considering everything is shorter in this game that's not really an issue.