I have been doing normal puzzles and puzzle rush on chess.com for the last 6 months. And I noticed that my performance in normal puzzles now jumped from 2100-2200 to 2400-2500. However, in puzzle rush, I still perform between 20-30 puzzles in 5 minutes without any noticeable improvement (like scoring more than 25). I'm still performing like low 20s and mid-20s sometimes, and rarely 29 or 30! I feel like I'm slow. It's true that I spend my time on normal puzzles: like I take 1-6 minutes (my average time is around 2-3 minutes) before I see the solution. I feel that normal puzzles improve concrete calculation skills, while puzzle rush improves pattern recognition in general and intuition for tactics without calculating deep enough. I would really appreciate some feedback on how to improve in puzzle rush because I think it can benefit my bullet skills.
I am not very good at puzzle rush, but in principal it can be that 6 months are simply not enough to develop a complex skill. It is also not uncommon, that progress happens "in jumps", this has happened to me and was reported by others. You may try to give you another 6 months and then see what happens.
Keep in mind, that puzzle rush was invented by chess.com and is not in line with old school recommendations, of how to improve in chess. Typically an old school GM will condem blitz playing sharply.