Isn't that a failure of the framework developers that not more stuff is in reusable libraries? When I did some Angular I thought that at 70% of the framework should be in libraries that are independent of the framework and reusable.
You need framework integration at some point; otherwise, you end up writing glue code for every single library you use, which is a huge waste of time. The issue is when some library authors don't separate the "core" part of the library from the framework integration, but that's understandable because 1) it's less work to only support a single framework, and 2) you can design your API around that framework specifically, as opposed to trying to make something generic (which often doesn't translate well to some frameworks anyway).
I think the idea was to keep it as a library rather than a complete all-in-one framework. It has it pros and cons