Well certainly part of it is much of the .deb ecosystem still feels like its stuck in the late 90s linux era to me. But maybe I'm alone on that gut feel.
I'd like you to explain this a bit deeper. As a user from the '90s I am quite happy with it, but I might be stuck in my ways, who knows? So not saying you're wrong, but what are we missing exactly?
there are distributions that provide rollback. but as far as i can tell they require you to keep the old version to roll back to, stored on your computer. you can't roll back otherwise.
i really want this to work like revision systems for code, where i can just checkout any old version that was committed.
another feature that i would like to see everywhere is stickiness of the packaging source. currently, if i include additional repos they override the main repo, such that always the newest version is picked from any repo.
this makes it difficult to include less trusted 3rd party repos. i would like to be able to add 3rd party repos such that only the packages that i explicitly install from that repo will also be updated from that repo, while any other packages in that repo will be ignored unless no other repo has them.
in debian it is possible to set priorities for different repos, but that is not easy to manage. the priorities to have each package update stick to the original repo should be default.
guix and nix do provide some of this as far as i can tell, but i am not a fan of keeping every package self contained with massive link trees. (i may change my mind on that some time maybe, but that's what i feel for now)
conary was/(is?) a packaging system that did have both of these features, although, according to some of the developers the repository was a bit clunky and could have been better. but that was under the hood, not noticeable to users and packagers. i loved working with it and i wish foresight, the distribution using it had become more popular so that it would have had the manpower to keep going.