Yeah, I agree with this. For the lay person it's not going to work for backup, you need something else to checkpoint the files. Versions, ZFS snapshots (what I do), git, bash scripts + Backblaze, whatever. Lots of people don't want to mess with this, which is what Dropbox used to solve for. Now you're constantly barraged with whatever new methods they are experimenting with to monetize. But we know that, so I regress.
For those who don't mind a little extra work (I argue Backblaze is almost no work using their Web UI), syncthing is a really great solution.
And Syncthing repeatedly and very explicitly warns that it is not a backup system, and you should have a separate backup running as well.