> But it still seems important to distinguish "they broke the entire permission model, where I can no longer trust the sandbox boundaries" and "I'm locked out of crucial parts of my system" from "gosh, this is slower/more confusing than I might like".
Well, if they succeeded at that it means the permission model is broken, and you can not trust the sandbox boundaries, whether you have Dropbox installed or not. So no reason to be angry at Dropbox; ask Apple to fix the sandbox model instead.
Dropbox is not a sandboxed app on macOS.
I'm not sure the beta testers understood they were giving up that level of control by installing Dropbox's new software. The post's author certainly didn't.
True, Dropbox got away with grabbing permissions that apps shouldn't have, and then getting away with it. But it's still IMHO a bit more than a bug to take this attitude of "let's take whatever we can! It's Easier To Ask For Forgiveness..."