Then I try to close the program and get more errors, such that I have to go to Task Manager to kill it. Come back in and try opening a different project, same behavior. Then it gets interesting - I try to uninstall, and get messages about a bunch of things it couldn't uninstall on its own (like the redistributables, Azure, etc.). Try to reinstall anyway and come back to same problems.
Then I go through add/remove programs and manually uninstall a huge pile of c++ redistributables, reinstall, no change. Then I google a bit and find out about the cache folders in AppData/Local and/or Roaming, and delete them too. Uninstall/reinstall VS. No change.
I'm starting to wonder if I'm going to have to do a full pave and reinstall windows here, WTF?? I only had one bug to fix.

Would accept all forms of advice, hand-holding, or simply commiseration.