While it'd be nice to be able to run Linux on my M2 MBP someday when Apple stops supporting it, ultimately, the reason many (but not all) power users buy Macs is because they want the UNIX/UNIX-like work done for them and for it to run on fast hardware. If I want something more customizable, I'm barking up the wrong hardware tree.
Does that solve the question of "what do I do with this Mac that no longer gets updates?"? No, but most people either list theirs for sale to someone who isn't as bothered by that, or trade it in at an Apple Store for credit towards the new shiny.