That reads less like a reasonable, well-thought breakdown and more like a whiny diatribe coming from an entitled teenager. If the entire argument boils down to "I don't wanna!", then what's the point? Don't upgrade. Apple isn't forcing anyone to upgrade at all. If you need to run all your old software, don't upgrade. That's not a fault of the new OS. Technology changes. That's a fact of life. Even the example of Aper…
Is it? It's not really clear to me there's any sort of hard technical limit that requires operating systems to abandon components that support older software.
There may be an economic argument that every team has a limited amount of attention and resources, and older libraries/apis/layers may compete with newer ones, and that argument may even have some merit if the newer stuff is categorically better.
But, OTOH, there's MS's backward's compatibility, so it's clear that some platform owners can bear the cost just fine. Too bad Apple just doesn't make enough money for that, I suppose. :/
Perhaps they could think differently and charge users who want to stay on older versions of macOS for the updates. That'd provide a signal of how valuable it actually is and perhaps even a supporting revenue stream.
Unless resources aren't actually the issue.