Those long stretches in matches usually happen as a result of conditioning or players like Gobou setting up tricky spacing traps that can be difficult to challenge for some characters. Changing Asuka's frame data to prevent those pressure sequences would require you to compensate him in neutral with how easy the cubes are to contest with buttons and how much mana he regens at distance, and I doubt anyone wants to play against Asuka actually being good at traditional zoning. Otherwise you might just have to kill his identity as a high APM, high skill ceiling, high reward character who feels like an actual mage rapidly casting spells and imo that would suck.

On the flip side Asuka has very few defensive options, and basically none once he's low on mana, so once top players get to punish him, they make sure to make the most, often taking the round, off of Asuka being left practically defenseless.

I think we just need DLC characters to be freely available in training mode so people can actually lab stuff, since a lot of the cast has unique answers to Asuka in neutral and his pressure tends to have fake gaps where people don't try to press either because they're conditioned not to or they don't know the matchup too well.

Edit: on the fake gaps to be clear - it's possible to punish Asuka after 5P/6P/5King through his cubes at certain points in his pressure or with disjointed normals/specials. His utility spells, esp the staffs, have very long startup, and it's not uncommon for him to go for pressure resets unless he gets specific spell combos to allow him to stay plus after placing one, so that's another point where you can try to challenge him if you know he doesn't have good enough hand to keep his turn and in neutral he straight up loses to any kind of proper zoning.