I'm afraid you are right .
Ideally it would be an independent 3rd party Unix based OS, but the OS competition train has left a long time ago it seems .
Too complex I assume, and the market fenced off by MS and United Fruit .
Apple is too lazy to support more than a ball pen at this point, so no hope there .
Have a look at Elementary OS, it's a very mac-like looking option. I've used Windows 10 recently, but can't get over all the undifferentiated white in the window chrome areas.