What you chose to describe as "legacy cruft" is actually the luxury laptop people spent over $2K close 6 or 7 years ago.
> The alternative is you get to keep 20-30 year old legacy cruft, as with Windows.
It's not a choice between bricking perfectly good computers after 6 years or maintaining them for 30 years.
And heck, Windows 11 doesn't really support pre-Coffee Lake CPUs without hacks similar to OpenCore's.
During the past 3 years I was forced to upgrade from Mojave to Big Sur to Monterrey, each and every single time because otherwise my 2019 MacBook pro would not be allowed in the network as it was running unsupported OSes.
No, they do not keep running with the last supported version. Having a successful boot sequence and seeing blinking lights is not the end goal of spending over $2k on a luxury computer.