I think you maybe misunderstood why I would want a Demo.
There are two main reasons for demo's.
A- To see if you enjoy the gameplay/concept/etc
B- To test if the game actually runs on your system smoothly/at all.
The game looks amazing to me and I am pretty damn sure I want to play it.
My issue is the later, for most games it's the later. Honestly I often feel like game dev's have forgot about this concept..
Maybe you could offer the Mac version on steam?