> Could we revert abstract types in `typing` to respond True to `isinstance(..., type)` again?

No, making them classes will cause significant performance penalty (I don't remember numbers now, but importing `typing` may be twice slower). Plus this will re-introduce some bugs and inconsistencies.

> I don't want singledispatch, or any other library like it, to have to special-case typing.

I didn't propose this. I proposed to allow all objects that pretend to be types but are not actually instances of `type`.