I found that since LLMs can produce any code I want, I don't really feel the same drive to learn React or whatever is popular and trendy to make myself useful in a new job. Instead I feel like I have the space to play with something that I enjoy instead, like learning Z80 assembly and writing games for the Gameboy that I would have wanted as a kid. I think you're right that it feels just like going to the gym, intellectually.
Yes, but in terms of your marketability--even in a world with LLMs--it seems to me that learning React or whatever is popular and trendy is quite vital. You can't propose good architectures in /plan or review slop PRs in React without knowing React to a level of depth that could only come from having toyed with it, and thought in code.
It is still an open question though exactly how big the need will be to propose good architecture or review slop. I petsonally think it will still be important, but it will vary by application for sure.