How do you know that - have you played it?

It may not be "no gameplay," but it adheres to a very loose interpretation of "gaming." Whatever rules exist in the game basically only serve to aid the sense of progression as people continue to explore. Losing happens only if you explore in a manner that isn't careful, and winning happens when you've explored (carefully) to the center of the universe. [1]

The game isn't supposed to be a game for game's sake, in other words; it's intended to just be an adventure. "Winning" and "losing" are a means towards that end.

1: https://en.wikipedia.org/wiki/No_Man%27s_Sky#Gameplay

Same as it ever was. Anyone who's been paying attention since the beginning of video games knows that game play is what you make of it .. "It's not a very good game" has been said of many stellar successes in this realm, where the position usually changes after people have actually, you know .. played .. with something.

Because Devs said so. They have been hyping this game for over a year and still dont know what, if any gameplay there will be in it.