Depends on what you used, i guess. I bought an iMac in late 2009 which i think came with Snow Leopard and i upgraded to new macOS versions whenever they came ou

Depends on what you used, i guess. I bought an iMac in late 2009 which i think came with Snow Leopard and i upgraded to new macOS versions whenever they came out up until El Capitan which was the last version to support it (i've heard that you can run Sierra with an unsupported patch too but didn't try it). I've also got (some bought, others free) a few applications from their developers' sites - that was before the Mac App Store. After every single macOS upgrade some application would stop working. By the time i installed El Capitan, no application that i had installed since the Snow Leopard days worked. Mac App Store didn't help either though. I've only bought a couple of applications from there, but one game - NOVA 3 - broke after an OS upgrade (do not remember which) and then was removed from the store instead of being updated. Of course this is partly the developers' fault, but on Windows this would never have been an issue as i have games and applications more than a decade older than NOVA 3 that still work on the latest Windows 10 with little to no fixes. I also had a similar case with iOS - i got an iPod Touch some time ago, bought a bunch of things, several versions later nothing worked. Eventually the device itself stopped being supported and developers were both forced to not support it and did require later versions of iOS. Typical case of forced obsolescence since otherwise it was a fine device. This experience alongside Apple's attitude towards (ignoring) backwards compatibility is what makes me stay away from their systems.