I think the question is also, “good in what sense?” The really valuable skill (from a dollars & cents perspective) is to be able to provide business value to _

I think the question is also, “good in what sense?” The really valuable skill (from a dollars & cents perspective) is to be able to provide business value to _the business you’re employed at_. That might not transfer anywhere else. Eg I doubt my skills apply to a young startup- I’m a specialist (ML research), they need a generalist. If I work at Google on search & get really good at solving political problems related to search, that’s a super valuable skill set _to Google_ but probably not to anyone else. I’d probably get promoted and/or get big bonuses. It also probably means that, _ceteris paribus_, I’m a worse coder, as I’m spending less time focusing on tough coding problems.