For me, leaving a plateau usually requires a paradigm shift. Here's a few rabbit-holes for you:
• Learn memory management from Rust
• Study Postgres internals: https://www.interdb.jp/pg/
• Learn architecture and design from Elm: https://taylor.town/elm-2023
• Try building things "from scratch" with zero dependencies
• Watch online lectures from Joe Armstrong, Alan Kay, Gerald Sussman, Bret Victor, Casey Muratori, Greg Young, Richard Feldman
• Build a robot
• Learn a semi-esoteric language like Forth, APL/J/K/BQN, Lisp/Scheme, Wolfram Language, etc.
But research isn't enough. I never really understood the value of new paradigms until I tried to use them in a personal (or professional) project.
Let me know if you need any further resources or suggestions.
Good luck!