A standard optimization for reducing overhead is to Alpine based images.
Similar quite a lot of official docker images people base their images one are Debian not Ubuntu based.
And a lot of Linux server work in certain sectors is based around RedHat.
Similar docker gets in a lot of areas replaced by podman (through I guess for this discussions we could treat them as being the same).
Lastly outside of server space (and ignoring embedded Linux) Steam Os (Arch based) might have interesting effects in the future (due to the Steam Deck, which IMHO is very promising).
So I'm not really seeing everything written for `Ubuntu` only, through a lot of things will target Docker with whatever they like as a base.
Through then we would need to consider what we mean with "everything".
I mean the situation around Games, multiple Server scenarios, Embedded Linux and multiple scenarios of desktop Linux differs. Sometime quite massively.
E.g. Linux Gaming is/will be eaten up by proton, independent of weather it's proton on Steam Os (Arch derivative) or proton on Ubuntu. Similar in a University related context the large majority of people I meet which did ran Linux did ran Ubuntu. But outside of a University related context it was pretty much the opposite and no one I meet ran Ubuntu (anymore, may did in the past, e.g. in University, but switched and stayed away from it since then).
E.g. if the Steam Deck is not just successful but also stays successful then in a few years more "Desktop" Linux systems might run Steam Os (Arch derivative) then Ubuntu (partially because the university Ubuntu share seems to be eaten up by Windows and their subsystem to some degree).