Yes I don't think you can/should rely on TM only. It's convenient to keep running in the background but you'll still want to do manual backups to multiple places (external disks, Dropbox, Github etc)
As an aside, I’m surround by people who consider cloud syncing to be a backup, and just yesterday witnessed someone in the grief stage when they deleted a load of photos to save space because they thought they would remain in the cloud. They had even clicked through the “delete delete? Are you sure?”.
It’s almost been enough to get me to have a test LAN and real one so as to maintain household tranquility.
When I worked there, I was surprised to learn that they also often act as mitigation for ransomware attacks (they could roll back your account in time if you contacted CS and explained your situation).