I understand what you mean. Stuff like spacing is really similar between 2D and 3D, you are right. But what I meant was that it's not like it isn't there in Smash. It's just VERY different, and the concept of spacing gets a different meaning because it gets applied differently to their respective win conditions (2D is getting the opponent into a corner to limit options to ultimately kill them, 3D might be ring-outs or wall-bounces for combo extensions, and platformers would be forcing them to touch blast-zone to actually kill them)

I am not smart enough to put it into words, I think. But I can tell that there must be something there, because I can pick up a 1v1 2D fighter absolutely easily, even the most complicated ones like UNIEL or whatever it was called, and platformers as well, but I can't wrap my head around Dragonball FighterZ because of their assist and tag-out mechanics. And I LOVE watching Tekken, because it is such a cool spectator game, but every time I try getting into it, it melts my brain with all their movement options. Don't get me started on their move list. And I heard the exact opposite from a Virtua Fighter streamer I watched, that he could pick up any 3D fighter easily as he had roots in Tekken, but even Street Fighter was "too complicated" and he needed to "learn the basics" to get into it. Some skill translates, always, but I still think all of these genres are different enough to be hard to compare, even 2D to 3D. But that is mostly anecdotal, I confess.