As an anecdotal example that may be relevant, I wanted to upgrade to Monterey and my Mac Mini said there wasn't enough room. Hooked up a Western Digital external drive that I had used on previous Macs and launched Time Machine. And that's when it started. Time Machine presented what seemed like a stack of Finder windows in the middle, a timeline with hash marks on the right-side and the only button highlighted was th…
I think your difficulties may stem from thinking of Time Machine as a backup application, when the UI is designed around treating it as a core system component. The configuration is all handled through System Preferences, and the UI you entered was solely for viewing and restoring files from your backup archive. You probably also missed a prompt to use the drive for Time Machine backups when you first plugged it in.…
The TM UI is solely about recovery. It backs up "everything" not on the "skip list". And out of the box it defaults to just the system drive (vs the system and external drives).
And that's an interesting facet here. This is a case of going in to a bookstore and scanning up and down the shelves and not finding what you want, and being frustrated, because you don't realize that you're simply in the wrong section. The TM UI in this case was frustrating because it had no options to do what the person wanted to do. And by design, it would not do what they wanted to do.
It's not a UI fault of TM per se, specifically this aspect of the TM experience. TM excels at full drive recovery, and recovering "a few, select" files. In the middle, it's not so good.
It's worked great for me. I've recovered from it several times, both entire systems and a few files. I use it solely on my main drive, and I use BackBlaze for the entirety of it all as a hat tip to offsite DR.
Over the years, I've lost a couple of TM volumes to strange corruption. Not that much of a crisis, I just reset it and start over.