I played Minecraft for an hour a million years ago and at the time it was basically digital LEGO. Since then I've gathered it has a campaign mode or something, but my entire experience with it is creative mode or whatever, when it was accessed and played via a web browser.
And yeah, I'm aware lots of adults play or played minecraft. I still play with LEGO. But that fact doesn't mean that calling LEGO a children's toy is wrong.
Also I've been active online since the early 90s; 15 years does feel like comparative internet infancy to me.