The idea of the Time Machine is good, but it's not well executed. From deleting old backups automatically for space (I might want to save some of those old things)
If you have something you want to keep, keep it. Don't depend on TM to know that you want it. The deleting old backups is a tradeoff; would you rather it fail to run a new backup due to lack of space?
to using a nth degree differential backups that depend on the root and the entire backup tree to work...
That's not the way TM works. No diffs are involved at all. It creates hards links to files/folders that didn't change since the last backup. You can delete older backups and files in it that have hard links from newer backups will be retained.
Each time it runs you risk corrupting something so bad the backups will be worthless. I'd rather apple would let me chose folders and just do full zipped/encrypted copies of those I choose. Time Machine just lulls most into a false sense of security
I won't dispute that TM can get corrupted. But you certainly can set up your own backup mechanism of files of your choice.