Well, top players are top players to a large extent because they are hard to open up, and are adaptable even under extreme circumstances. Hitting a really good player with the same mixup repeatedly is hard, because the very best players are themselves quite good at patterning/recognizing pressure strings and tendencies.
In terms of opening up top players, I will shamelessly plug this thread, where we talk about patterning (“the read”) and why people get hit when they do.
Basically, I suspect your pressure has a large amount of flowchart to it - “I have thrown you, I shall now do X”, or “I have a bird and an arrow coming down, I shall do Y”. That’s fine as far as it goes, but if there’s no more thought to it than that then you have no systematic way to shut down/punish options or bait the kind of defensive mistakes that you want to impose. Think of your pressure in terms of “what options do I wish to limit/punish”, and then structure your offense to force the opponent to eventually switch to a less good option that you can punish even harder.
Defensively, I think consistently playing top players is probably your best bet, because that’s the only way you can see and acclimate to the kind of dirt that you need to react to. Don’t expect to win your sets - play to learn and to see how your opponents handle neutral. Don’t vortex them to death; your goal is to get as many chances at neutral/defense as possible, so that the next time you play that character at that level, the things they are doing are all things you’ve seen before.