Every person I've seen online talk about it wishes to be you, everybody wants to experience it for the first time again. To unravel the mystery once again, to have the pieces fall into place and understand it for the first time again. As the other person said - you can complete the game in 15 minutes, but it'll take you 15h+ to understand how to do that. It's a wonderful little piece of art which nobody will tell you anything about - because they don't dare to ruin your experience of playing it for the first time.
It's about space, it's about curiosity, it's about discovery, and learning, and that's about how much I'm willing to say about it.
You just have to take our word for it. It's the type of game that comes once a decade and stays in peoples' hearts forever.