You seemed to be suggesting that people with 2013/2014 Macs should expect there to be major bugs with Big Sur on their Macs, as if it was their fault for not having a meow modern Mac.
You've missed the point. To average computer users, the way that Apple has presented major OS updates to users, is through the same control panel that minor updates and security updates are through. This mechanism hides minor updates, showing just the Major update. Thus uneducated users think they are installing a minor update. Have had this problem with numerous clients who accidentally upgraded to Catalina and lost important (to them) software, because they thought they were doing "the right thing" by installing what they thought were stability/maintenance updates.
If Apple's quality control is so bad that these sorts of issues are slipping through quality control, then Apple needs to a) make it clear that their major updates are major updates, and b) have a warning that updating might cause instability.
Yep they are. Windows 10 gets frequent feature updates, twice a year I believe. These work on machines going back to 2005/2006, and for people who had Windows 7, Windows 10 was a free upgrade for a deal of time. So yes, Microsoft is giving constant free upgrades to Windows 10 for very old computers. (and 2013/2014 do not qualify as 'very old')