Sure, but I wouldn’t expect an elderly user to be one of the people with the natural ability to nuke their OS.
I’ve daily driven Bazzite, an immutable distro, since July, and I haven’t seen the kind of Flatpak issues they talk about - or frankly any major issues, this whole experience has been way easier than Windows ever was with updates (it took me a few minutes to figure out Proton and Heroic launcher though). I didn’t know about the new Fedora update until I booted up and my lock screen was different. My experience is that Bazzite (and likely all of the other uBlue Fedoras) is fantastic and absolutely ready now.
That said, nothing is more stable than something like Debian. Unless you’ve got some hardcore gamer grandma I think the immutable distros are a solution to a problem not present in OPs hypothetical.
No, because eyeballs are meat grapes.