Rust Duplicati Restore is another one (inspired by the Python tool), also mentioned in the forum here.
The point is that as an open source project, people can build tools to read its format in an emergency.
You could be far worse with a commercial subscription backup that has none of this, and then closes.
You could do better if everything was a super common format such as exact file copies, or maybe zip, however the storage cost of having so much duplication will be far more. Such programs exist though.
Cobian Backup gets mentioned in the forum by people who really dislike having a complex file format. Cobian Reflector is a more recent tool, by the same author who sold his program then reimplemented.
There are others as well, but they give up lots of capability in exchange for a very simplified approach.
Duplicati is a backup tool, not designed for (and maybe not reliable enough for) archiving for decades. Technology always changes. For easier access by descendants, laser printed paper can last awhile…