Have you tried to compile with MacCatalyst? It doesn't provide full access to any iOS framework, but it basically is a good option to get started (instead of re-writing all the UI code for the Mac). You may also write special code for the mac to get around framework limitations (some aren't available). But before you try, do yourself a favor and create a special branch for testing. ;-)
You can use a 9 year old operating system, but if your computer has an Intel processor, it means that it is useless garbage that can't be used for anything and has to be thrown away? Fortunately, that's not the case. It would be very annoying, if my special configured €4500 MacBook became useless over night. No one gonna fool me that my computer is outdated and can't be used anymore.
I'm just throwing some wild ideas here, but could it have something to do with an attempt to increase sales of new products? You know, like when they stopped including earphones and charge adaptors with new iPhones, saying it was a necessary action for the environment. If you ask me, you gotta be born behind the barn to even believe in it haha.