Here's my €0.03:

I really wish Linux distributions started adopting a similar model to the BSDs. Ship a base system that's minimal but rock solid; stick to LTS kernels, etc. Issue patches/updates for security issues ONLY. Ship another major release once or twice a year. (Fedora Silverblue is kinda going in that direction.)

Everything else? Pick from Flatpak, Snap, or AppImage, but just go all-in on that. Focus all development on making the experience first-class. Let Gnome, KDE, etc ship their own builds.

The tricky question is how much to include in the base system vs Flatpak. It's kinda-obvious that for workstations, the installation media must ship enough GUI to get you a functioning desktop, a web browser, and an app manager ("store"). OpenBSD's base system includes X11 and a couple basic WMs, but the story is a bit more complex if your target audience is less technical.

This path would kinda dilute the difference between distributions, but that would actually be good for them. I already tell friends, if you want to try Linux, just pick between Ubuntu and Fedora. They're both OK.

Servers? Go all-in on Docker/Podman. There are plenty of existing distros that do exactly that.