I got the impression that 5 minutes weren't enough time for Sean to explain even the core aspects of the game...
He said at the end: "Trading, fighting, exploring, survival." That's pretty sweet, actually.
The reaction was muted because the presentation wasn't the "all-out HERE IS THE GAME"-showing. It was a humble attempt to try to get across the game's scope.
No Man's Sky needs a longer gameplay video with commentary throughout.
Well, we've only seen a tiny portion of that planet.
I think for a development team of 10 people this game is shaping up to be something incredible
Edit: Man, now I do sound like I'm defending the game