I used to scoff at various art forms (paintings, music, dance, etc). I too am at your place. Extremely involved in a multitude of activities in youth, cold pressed into an engineering job at a big company.

> I feel like my intelligence has been reduced to the next lowest standard deviation

I used to have this same feeling. Especially after watching my junior engineers work through stuff, both in office and online. A lot of self doubt crept up into me regarding my capabilities.

Then I started getting into stuff like arts, politics, physics, etc. I have a natural love of paintings. Reading books about paintings, learning their history, etc. to keep me occupied has helped me a lot. I can't pin point exactly, but I felt more confident. I expanded my leisure by completely stopping any TV or videos (I avoided buying a new TV when moving away from my parents house) and just reading and listening a lot about a wide variety of topics. Engineering, Astro Physics, Painting, Culture, Politics (But not sports, I hate sports). I do it just for 30 - 45 minutes a day.

Maybe it's just me, but I feel more confident. I am not even sure if that's the reason for the confidence.