MacOS software updates are free. The issue is that suddenly Apple decides your perfectly functioning computer is no longer supported, and after that in a matter of 2 years you will no longer find any new software for your OS, and then you have 3 options:
Buy a new computer.
Hackintosh it with a dosdude patch to use the latest version of MacOS.
I think they're referring to the fact that you can only continue using an unsupported version of MacOS for two years, not that the computer will only get two years of support.
I'm mostly fine with it because my work buys my equipment so asking for new hardware is easy. Buuut you are absolutely right that we need a systemic fix for this. It's anti-consumer for there not to be some required support length of like 5 years or something
I have been replacing work laptops every 4 years and home ones every 5 to 6. I've never had an os update issue. I suspect your concerns are more than 15 years old.