You think you're better than you really are, and that's it's a wall. I'm sure you have tons of C and B scores at even 4* maps.
All your topranks are the next: Long easy maps or really short ones. Typical map style where you got something like 80% to 90% jumps, 5%-15% streams. There are maps what are just the opposite, stream maps, tech maps, finger control maps... Try improve like 4* stream and tech maps until you can start farming 5* maps. Also practice 7* spaced easy maps. So you mostly start to be able to farm any map without limitations. Play more 4* DT maps. There are 300PP maps like Orange insane DT what you may be able to fc after a few weeks of practice. Increasing your speed and aim, enought to start to fc 6* short maps 250PP+.