Yes, I would say that is correct! Like I mention at the very bottom of the README, Refurb is not meant to be an all-in-one linter or formatter: Tools like black, flake8, mypy, etc. already exist, so trying to recreate what they do would be a lot of work. Refurb is more of an addition on top of the tools I previously mentioned, and less of an altogether replacement.

Related -- I'm curious how you'd compare this to pyupgrade https://pypi.org/project/pyupgrade/

Interesting, I have never heard of this project before! From looking at the README, Refurb is more focused on simplifying the codebases, making them more expressive, whereas pyupgrade seems to have the goal of upgrading you from version A to version B (specifically Python 2 to 3). Near the bottom there are some newer Python version (3.6+) related upgrades, which I was considering adding to Refurb. I expect there to be some overlap between my project and some of the existing projects out there, so I will have to weight the costs of adding these in vs leaving them out.

Thanks for mentioning that project!