CLN: Replace isinstance(foo, Class) with isinstance(foo, ABCClass)
- [x] ref #27353
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Nice idea but I don't think worth changing this. Looks to be compat code which I assume we will get rid of soon anyway - @TomAugspurger may know when Agreed with @WillAyd.  I expect the failing tests are because this puts an unexpected name into the top-level namespace. Closing for now since I don't think there is a desire for this one, but thanks anyway @MomIsBestFriend 