> It changes too much, stuff gets dropped too often,

Stable features that are visible from user space? That would be extremely surprising.

> it's buggy, it's insecure as hell

It's really not. It has bugs, even security bugs, but no more than any other modern kernel.

> there no test framework.

https://www.kernel.org/doc/html/latest/dev-tools/testing-ove... plus assorted fuzzing and integration testing