Polymathy or Jack of all trades mentality is the new self-help. Ever since I started this journey in 2022, I've become a better writer, more fit, and motivated overall.
I recommend building your polymathy journey like RPG stats. Your five stats are: Strength, Intellect, Creativity, Spritituality, and Charisma. Then you tie your hobbies together with these stats. If you feel like one of your stats is low, then you practice it.
Reading Range and Thinking Like Leonardo Da Vinci will also teach you to think like a multidisciplinary thinker. The hardest part of this path is balancing your time, but the trade off is amazing. Even though I'm not a super-genius, I feel like I can do anything I put my mind on.