For instance I see a lot of developers and engineers with 6 months and more experience with functional components and still misunderstanding the point of all of this. And these are smart people at high tier companies.
The main thing being the meaning of having dependencies for useEffect and other hooks.
That said, it isn't a smooth transition going from explicit lifecycle methods in class based components to useEffect hooks in functional components. But it refines the quality of the thinking, and the quality of the code overall, imo.
Specifically, how are useEffect dependecies complex? You list the variables that, when changed, should trigger the hook to run. What am I missing? And I'm not claiming no one struggles with hooks. But people also struggled with the lifecycle methods of React classes. In almost every case I've seen this, I've asked the developer to read the React docs. That's usually enough. I'm guessing there is some other underlying more fundamental issue if someone is still struggling with hooks after six months of hand holding.
This is 100% a result of how react (ab)uses the host language semantics to implement their DSL to describe components and has nothing to do with the conceptual nature of functional components themselves.
It relatively easy to imagine a design that doesn’t require the dependency lists when capturing a callback closing over props or state.
Not saying that design would be better or worse, just that it could exist and still leverage concepts like FCs, hooks, effects etc.