I'd add lack of flexibility as a huge downside for me. No way to sync external drives to Dropbox, even though their common 2TB plan is way bigger than most laptops' builtin storage. And no way to sync any files on your primary drive outside of the main ~/Dropbox folder. I always want to sync certain configuration settings so that if I use the same apps on multiple computers, or get a new computer, everything just works the same way. Syncing symlinks used to be a decent workaround for this even though it was never officially recommended, but they killed that ability and never replaced it with any other solutions.

Now I've switched to iCloud, where I can more easily back up my full machine, and which syncs my Documents folder by default which is where a lot of Mac apps have started putting some configuration files. It's also a better replacement for Google Photos which is shutting down its free storage soon.

It always felt like Dropbox was too eager to play "me too" with all the other cloud service offerings, and not only did they not particularly succeed at that, but they kind of gave up on their own core competency to do it.