I think that like it or not, Docker has managed to win mindshare in a way that no single distro's package management ever did. Application developers could never get away with publishing only RPMs or only debs (and whether the same deb would work on Debian and Ubuntu was always a risky question), but everyone runs Docker; even the alternatives like Podman or Moby feel the need to be compatible with existing Docker packages.

Yeah, that's probably true among developers. Among other classes of users, providing a deb or an rpm (or some combination of package manager formats) has been pretty normal. Enterprise software like Slack has been doing this for ages, Microsoft distributed Teams that way for years, the CUDA stack is rpm/deb, etc. Outside of the dev world, docker is basically a signal that your devops people should be on the project. The most common question used to be "why no installer" but nowadays users just use the "app store" (Gnome's Software or KDE's Discover) to Get Stuff, and wouldn't be able to tell you if asked whether what they just installed was a native package or a Flatpak.

I do agree that Docker is ubiquitous in the development world, but I think the fraction of people even aware enough of packaging to have an opinion is vanishingly small.