There are ways around the official support drop as well, I run macOS mojave fine with a Mac Pro 3,1. These original cheese grater macs are truly still the best desktop tower they'll ever make at this point. It'd be fun to trick one out with a 3rd gen threadripper, which is probably faster than the 28-core rumored $35,000 mac pro.
I get where you're coming from but the whole point of getting a Mac is "it just works". I just don't have the time to deal with a Hackintosh. Also from past experience, there's a reason why they sunset older machines. At some point the OS updates are just no longer compatible with the old hardware. The Mojave patch notes that you linked further confirms this.
Another issue is that Windows 10 is now at the point of working decently and it has Ubuntu baked in. Apple also has iCloud sync software for it. I will miss Mac Apps, but given economics, most people just crank out electron apps anyways.
I give up on Apple computers. imo There's no viable option for iPhone or iPad though, so I'll still will be with Apple on some level.
I'm not sure if you can say Macs just work anymore, and obviously this is the realm of people who like to tinker or make things work for the sake of the process. If only there was a word for it... Oh wait I think it's up up next to that Y up there :)
The old hardware is pretty well supported in the Mac Pro because of how modular it remains. The majority of the incompatibility comes from not having a GPU that works with Metal. Those patch notes are mostly for devices with soldered components, like the GPU.
They don't just work any more; I have an older cheese grater mac pro; and new video cards for it are a dismal lottery.
You could say this is why a modular Mac is a bad idea.
My Apple MAC SE; still just works; it runs Word 5; which is all it ever did.
Here's the patcher: http://dosdude1.com/mojave/
There are caveats, but I've found it to work well. Of course it's totally unsupported so here be dragons, etc.