Guilty. I'm pretty good at my job, but I never learned CS fundamentals and don't work in a context where this matters (I currently work in front-end JS/TS).

I don't think it's worthless knowledge to me, but I think you're a bit blinded by your own context. I have seen many comments on HN bemoaning "Developers who don't even know X", and X is always something different.

I don't think there's a smoking gun for bad developers and it's weird to me when programmers think there is one, tbh. Everyone has gaps in their knowledge, and with something so arcane as programming, it's very easy to have no idea that you're missing some important or "fundamental" piece of knowledge