They likely need a monetization model in order to pay developers.
And then later I learned it was a cooperative effort, just not under the same name
Source?
They developed the "privacy sandbox" together.
Yeah that's not true.
You have to remember that sometimes when that shiny new CSS feature comes out, it is underspecced, with unhandled corner cases -- "just do what Chromium does" is not a standard -- or is it? Having multiple implementations of a spec prove that it is interoperable - without that, you might have a good spec, or you might have a spec that says "whatever Chrome does is what is expected". Not sure that is what we want from new CSS (or any) features.
The 2FA thing sounds like it's all on the Dropbox side if you are just entering a code you got from an authenticator app. The Google login issue may be a real issue -- did the Google login specifically work on another browser?
Uhh, that doesn't seem normal at all. Is this a default config? Any extensions in use?
Probably simpler to just "Forget" the site from the site's context menu in the history sidebar.
What are you a captcha?
This is fine and all if you have some low-end device without gapps, but... run Firefox Nightly. 😉