Isn't this true of gnu/Linux as well though? A lot of patches are drivers and fixes? For example, one could argue trim for solid state storage is a driver issue?
Of course it is. Drivers will be the majority of the work in any OS that is not locked onto a very limited set of hardware.
I think this is the case with both Windows and the Linux base distros. It's a necessity when you need to support a wide array of hardware, but might be different with Apple's ecosystem.