Joel, you’re definitely right that file sync and backup are not the same thing. But our experience has shown the file size and name restrictions aren’t a big issue for most users (now that MS has addressed most of the common tripping points from the past like increasing the individual file size limit to 10GB, allowing path lengths of 400 characters, etc.). That’s not to say there aren’t still some issues, just that they tend to be few and far between in our experiences so far.
As for ransomware issues, MS recently announced a new feature that allows an admin to ‘rollback’ a onedrive to a recent point in time specifically to deal with this possibility. You could always call support before and have them do it, but soon you’ll be able to do it yourself from the admin GUI.
Again, I agree it’s not a backup product, but we find it’s ‘good enough’ in that capacity for most user workstations and brings lots of other benefits to users like mobile/remote access and collaboration options that backup solutions don’t provide.