Linux Desktop evangelists have been saying this sort of thing for about a decade now, only they used to exclude "games" from that list because Linux was so terrible as a game platform. Their constant underestimating of "average computer user" is, in my opinion, one of the big reasons they've completely and utterly failed to make significant headway in the Desktop market.
I stopped caring what most people use. I prefer to use Linux and OpenSource software in general for myself but I don't push it onto others. It doesn't matter if the market share of Linux is 1%, 10% or 50% as long as it works for me - and it does.
For example Ubuntu is getting very close to that point already. They stuff lots of stuff in it that I don't want (like snaps) and make them really hard to disable completely. Exactly the kind of thing I left Windows and Mac for (as daily drivers - I still use them for my work)
Thanks. This was indeed my main point.
Of course this doesn't mean there aren't a lot of niches that require a particular OS.
I think 90-99% of users only use Browser+Office+Games which could work well in any of the big operating systems. Some software preferences are superficial and appropriate replacements exist on the other platforms.
As someone working with macOS, Linux and Windows I focus my workflow on the things that work under all of these operating systems so the impact they have on me is very little. People who are deeper into the UX of a single operation system may disagree completely.