They're not even a "folder that syncs" anymore, at least on android if you make a folder "available offline" (which should be the default to begin with) it stores it internally to the dropbox app where it can't be accessed by other apps. There is another button "Save to device", but that's just a one-time snapshot of the file that won't stay in sync. I deleted my account after they pulled that enshitification.

I am fairly certain that this was forced on them by google rather than a deliberate choice. Syncthing and other apps were put in the same position.