It's not popular because it's not realistic in most environments. In many cases it's advantageous to use those things you listed because that's what the market can provide talent-wise. I'd rather deal with learning new tech that's well documented than some custom lib that "just works" but no one understands because the architect left years ago. My whole career has been about consistent education, so that doesn't intimidate me. Working on undocumented architectures that I have to make substantial changes to (and not knowing all of the side effects) is what intimidates me.

Turnover is a reality that can't be ignored. New people come in and now have to figure out something that reads like a stream of conscience. It isn't well documented, doesn't follow the latest best practices and doesn't support modern paradigms and uses outdated frameworks/libs, but works great.

The apps I build always take into consideration the talent pool my employer intends to pull from. The reality is that they (usually) can't hire general "technologists" that are proficient at all layers of the stack. If the project is something that only you will ever work on, then you can do whatever you want and this whole conversation is moot.