You can stay on an older version for a little while, maybe a year at most until it stops getting patches. Then you get to make the choice of using an OS that's vulnerable to exploits and an OS with a gigantic backdoor in it.
Ah excuse me for that. 2 years of additional lifespan is still painfully short for a deprecated OS. Even free OSes like Ubuntu LTS get more years of support than versions of macOS (Ubuntu LTS release cycle of 2 years minus 5 years of support = 3 years of additional support after deprecation).
