While it may seem like Apple is proprietary, its no more proprietary than Windows. It's more like a car company since it's vertically integrated.
It is proprietary when you want to repair one. Apple has to repair their stuff, and they will only do it if they feel like it. On a generic, Windows desktop machine, there isn't any component inside that I can't easily get. Dells are a notable exception, but I don't buy them.