Turns out Google has been ruining Drive's speed by ramming Gemini down our throats (again). To get stuff loading quickly again, follow these steps:

From the Google Drive page, go to settings (top right, gear icon). Drop into "Manage Apps."

Find Gemini and uncheck "Use as Default." Of course it's automatically turned on despite my organization and my personal accounts having already opted out of Gemini. Once it's off things run much, much faster.

Presumably they're doing some dumb shit and having Gemini scan the contents of your entire drive, constantly.