How do you gitgud?
You're not going to get a satisfying answer to this question just by asking it like this, because in order to get good you first need to understand what exactly you're bad at. Different people will understand different aspects of the game differently, they have different gaming backgrounds, differently developed reflexes, they pay different amounts of attention to different things.
If at this point you can't take some specific parts of the game (whether it's some boss fight, a class weapon, or even a particular repeated occurence that leads to your failure) and ask yourself "What am I doing wrong there", a good start would be to record yourself playing different kinds of content. You might be able to figure something out on your own, but it's better if you have other people look at it.
I've seen people do some really bizarre mistakes, like holding technique charges for 4-5 seconds, saying that they couldn't memorize the timing, even though at that point they could just react to very clear visual and sound cues. I myself for the longest time preferred staring at my character to hit JAs instead of memorizing the timings so that I can pay attention to mobs that are trying to kill me. Managing attention overall is a very important skill (in life in general, even); in modern world people have their attention directed on autopilot to whatever may provide an immediate dopamine fix. Modern games in their rush to provide satisfaction as quickly as possible end up encouraging tunnel vision, and quite a few complaints about combat I've seen on this forum (like animation locks or enemies not having health bars) are often a result of people not being used to thinking ahead of what's right before them in any given moment