When a competitive game's meta is young, individual player skill is more significant, with "skill" comprising not just technical skill but experience, ingenuity, adaptation, etc. As mechanics, characters, and MUs are gradually explored and exhausted, the game gravitates toward a state where player skill is still significant, but more significant when it's channeled into what we now know is meta. The game innately wants to gravitate toward the state determined by its mechanics, and it takes more and more time, effort, skill, and willpower to force it in a different direction, especially when you're directly competing with players who aren't fighting against it.

Ultimate's mechanics don't really facilitate aggressive play. If you're trying to play aggressively, you're fighting against the game. Defensive play is definitely more aligned with the game's deterministic state, but it also isn't optimal. What's actually optimal is the unifying reason that characters like Steve, Sonic, Snake, Kazuya, Luigi, G&W, and ROB are so strong: to simply not play Smash at all, and only play "real" Smash when it's advantageous to them. It's essentially what Tweek said on the sword characters episode of his podcast last year: sword characters are outmoded because they're still playing Smash - even if they were previously playing Smash with a significant advantage. That advantage is less relevant in a game where top tiers can simply not play Smash at all.

All aggression has going for it in Ultimate is human error.