> Good companies

Good companies want both good coders AND coders with experience in the language or the plateform they use.

Not so good companies have a mess of broken systems. You end up spending more time reverse engineering random bugs in the systems than actually doing any forward progress. Knowing the bugs of a specific framework thus becomes a precious skill.

>They don't care if you know the framework or even the language.

Good luck telling that to a recruiter.

"Oh looks like you don't have 5 years of experience on a super esoteric framework released last year. Great we'll talk soon."