iPods and AirPort Express units from 20+ years ago still work in modern macOS too. Things have been shuffled around some (iPods are now managed with the Finder instead of in Music.app) but they still work.
replyI would agree with the idea that they're not bothered about breaking workflows, particularly those involving command line tools, but hardware compatibility isn't nearly as bad as the internet might have one think. Source compatibility isn't all that bad either, many ancient Objective-C/AppKit codebases can be made to compile in an evening. It's mainly binaries that break.
Yeah, Apple is very weary of breaking user functionality. They'll just break your app's ability to run.
replyFrankly, I don't think it's practical to expect operating systems to continue to run binaries perfectly in perpetuity. It's an enormously burdensome expectation that holds development of the platform hostage.
replyUsually all it takes to keep one's software running on macOS is compiling against the latest SDK once every ~5 years. Depending on the nature of the app, source changes often aren't even required. As a dev I don't think that's too much to ask.