Yeah, packages for things like Blender and Steam do exist in most distro repositories. But they make no distinction between packages that provide software like that and packages that provide core OS services + userland (systemd, pipewire, coreutils, cups, a desktop environment, and so on). What you want requires a distinction between those things.
See SteamOS, Fedora Silverblue/Kinoite + universal-blue, openSUSE Aeon/Kalpa, Endless OS, and possibly in future Ubuntu Core Desktop as examples of modern systems (or systems in development) that make use of traditional packages as the building blocks of the base OS, and then lean on application distribution methods like Flatpak or Snap to provide desktop software. Use of the distro package manager for software like Blender is explicitly discouraged by all of these.
Distro specific fixes and configurations shouldn’t be necessary as long as the OS provides what the application platform needs (desktop portals, audio server, display server, print server, message bus, etc) Flatpak doesn’t even prevent distro specific repositories if it’s really necessary either; Fedora ships with their own Flatpak repository in addition to Flathub.
You want better control of or isolated and relocatable end-user software installation, and it already exists - it’s just not being done at the traditional package manager level, and I haven’t heard about any development effort going towards changing that.
Those distros are different than what I am talking about. Those are immutable distros that preserve the preinstalled system base. It’s not at all what we’ve been talking about.
You’ve decided that it has to be the traditional distro package manager providing the solution - but that isn’t going to happen, because those have been designed to manage a single installation of interdependent software with no distinction made between core system libraries or services and end-user applications. The solutions to the problems that come from that - which also make it extremely simple to fix issues like the one you have using a single config file - led to the development of Flatpak and Snap.
Some traditional mutable distros also ship with Flatpak + Flathub configured out of box and present them alongside and with equal importance to their own distro-specific packages - e.g. Linux Mint, PopOS, Clear Linux, CentOS, and Fedora Workstation. And Ubuntu is pushing Snap. So they’re all unlikely to start putting work into enhancing their distro package managers to start providing the desktop software specific features that you want.
I don’t have hope for Linux becoming a major desktop OS anymore. It doesn’t seem like a priority. So I agree, distro developers trying to create an environment that would win over the Windows crowd seems like it would never happen because they don’t care to. It’s fine, different oses for different use cases.
