Then you still don't have the grounds to say this is disappointing. You can only be disappointed when your expectations are really high. I don't know how you can expect lots of scenes when this is a 3D open world and he is only ONE developer. Even then, he said not all the scenes have been added, which is why this is in ALPHA.
The things you can complain about are physics, UI, bugs etc. It's like someone paying a single baker to bake a pepperoni pizza, getting the pizza then complaining there should've been more pepperoni on it.
What bothers me is the entitlement some people here have and are unaware of. You're getting something people have been paying for years. I am one of those people, and it's a spit in the face when people go 'not enough content' bla bla bla. The effort this guy alone put in to even release an alpha like this is merit-worthy.