This is an extremely niche problem that is probably not a factor for the vast majority of people: but my organization uses a shared dropbox account for file storage (yes, yes I know). The linux dropbox app does not have the smart download feature where you can see all files and folders but don't need to have them local unless you request them. The only options are to either download the entire dropbox folder, or to selectively sync certain files and folders, and then only be able to see those files and folders.

Given that the dropbox is some 4TB, but I often need to access things that I didn't previously need access to, this is a bit of a deal breaker.

You said it in your first sentence: you know that Dropbox is not designed to function the way you're using it. That's a kind of tech debt that may (will?) bite you in the ass eventually. Linux being incompatible with the way you use Dropbox is just a symptom of poor infrastructure and security practices, though I understand that it's probably out of your hands to fix.