Me: Let's use some framework to make things easier and faster!

Boss: No, we will do everything on our own, because when you quit your job I won't find anyone who knows that framework to replace you.

Me: But you won't find anyone who knows our custom solutions even more...

Let HR take care of it.

Here we already had job advertisements asking for experience for an internal framework....

Been there, done that. When some senior developers are leaving the company, almost always documentation for the internal framework goes with them. Moreover - why the heck would anyone want to build yet-another-framework, where there are production-grade ready and verified tools available?

Had that same boss. Building everything custom and then expecting continuity if I get hit by a bus? Nonsense.

Boss is shit, both things will need a learning curve.

Have you guys read about the fact when you start a new job, you start from scratch, all previous experience is irrelevant you are the new guy, things are done differently, your voice does not count as much as it used to be, etc, etc.