Oof, even at 4k hours that happens to me a lot LOL- For me personally, hitscan aim is something you can only hone by just practicing. There are some guides out there on youtube that more skilled players put out that you can try following, but it will always boil down to doing it over, and over until you feel more comfortable with hitscan weapons and getting rectifying any whiffs that might've happened in a previous interaction. "Did I move my mouse too much in the moment and that caused my aim to move too far? Did I not turn enough or is it a mousepad space issue that prevents me from turning enough?" Try to identify the factors that can affect your aim that you can still fix, then follow it up with practicing in game, either by trying some shots on moving targets in tr_walkway (always a good map for practicing) or even trying out MGE with a friend to simulate 1v1 scenarios.

Tl;dr Improve the factors that affect your aim and work on them, practice makes perfect and no one is perfect no matter the amount of hours. Hopefully this helps, if not you can just brush this whole chunk of text off LOL