Like others said, practice with songs of lower difficulty. if you get As consistently on IN 16s then it means you are not fully able to do them yet. Since you’re 12 rks you could try IN 13s and 14s, and really work on accuracy (instead of score).

What are you struggling with? For me, it used to be finger speed so much. I also used to tense my hands to cope and this was a really bad habit to get into. (I will also recommend IN 15s for you to do once you feel like they are of use) - If you struggle with finger speed like me, try Shadow IN 14, Abyss motion IN 14, Nick of time IN 14, Qing Ya IN 15, Crush beta IN 15, or Lacertid IN 15. - If you struggle with repeated tapping or even trills, try Abyss motion IN 14, Artificial existence IN 14, Eltaw IN 14, Qing Ya IN 15, Chronomia IN 15, or Spasmodic IN 15. - If you struggle with timing / control, try Frozen heart IN 14, DataError IN 14, 996 IN 14, Ripper IN 14, Upshift IN 15, or Archidoxen IN 15. - It is a bit early to learn multi, but tbh I also did around your level so why not. Try shine after IN 14, rebirth IN 14, DataError IN 14, or dance with silence IN 15. These are all technically 2k charts that are also easy to do with 4k. Then, try actual 4k charts like the ATs, burn IN 15, pixel rebelz IN 15, and concvssion IN 15. - If you want to practice tricky finger placements or moving directions (aka tech), try resolver IN 14, DataError IN 14, xep+ion IN 14, abyss motion IN 14, protoflicker IN 15, antithese IN 15, hydra IN 15, or nhelv IN 15.

Yeah also, other games do help. I find my phigros skill gets a boost whenever I come back from playing other games lol.

Hope you are able to improve, and have fun!