Dec cleanup
- [X] closes #18190 
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

This should be the last commit to close out the issue referenced above. I think there's further opportunity to convert some of the imperative ``pytest.skip`` calls over to the new decorator methodology (especially Ibn ``pandas/tests/io``) but to keep the scope clean I would rather open a new issue for those rather than continually update #18190