[crimsonalucard1]

>but up close the details of say, managing state with hooks in React, is very different from managing state with services and RxJS observables in Angular.

I would say learning the detailed difference when needed for the project is in fact extremely trivial. The wrong kind of learning is thinking that you're improving your skills by memorizing and learning all of these details even when it is not required by your current project.

I would say max it takes about 2 weeks to a month for a developer to get good with react. It's not even a big deal if you think about it, but hiring managers still look for "relevant experience."

Don't learn the details unless it's relevant to the project. To improve your overall skills as a developer: Learn the fundamentals.

Though I have noticed one thing. Many recruiters and even technical hiring managers are buzzword driven. Buzzwords are often related to details so to pad your resume you have to learn the details. Ultimately though, if you end up never touching that detail or that detail changes then you wasted your time learning it.

Learn the fundamentals because the fundamentals never change.

Honestly you're the kind of developer that the OP is talking about, but then again most developers are like that.