I've found the same thing. Learning design and architecture really helps. Also, reading books from authors that have been around for a long time helps impart knowledge that isn't so ephemeral.
Learning functional programming has helped as well. Not that the language I'm learning is so much better than anything else but that it introduces me to new ways of solving problems.
I also want to invest in my writing. Good documentation is becoming more valuable to me as I age.
This is a very good tip and something developers realise with time.
What is DDD?
Domain Driven Design: https://martinfowler.com/bliki/DomainDrivenDesign.html
I have a similar story of study and my escape has been to learn more about software design instead of frameworks or libraries. For example; DDD teaches how to describe problem spaces and how to talk about solutions in a way that is independent of any particular language or framework.
My learning efforts now seem better spent on building a core set of knowledge that has broader applicability.