It's not hard to draw the analogy that Minecraft is essentially "advanced Legos", and the prevailing view certainly is that Legos are primarily for children.
Why that's the case is a separate question, but I don't think it's contentious to say that most people assume Legos primary audience is children.
1) Those building railways, roads, cities, redstone circuits, efficient automatic farms.
2) Those playing on "PvP" servers all day, attacking each other, fighting in arenas, clan wars, etc. (If you hear a constant "click click click" noise, that's probably them)
The ratio of type 2 to type 1 players is probably something like 7:3.
Type 2 relies on servers, while type 1 can be is usually done alone (on a server it typically ends in drama).
Guess I'll have to shut down my servers now…
None of us can commit the time we used to commit to games (a few of us have kids), but I reckon we each probably put in half hour to an hour every day or 2, and the occasional 2-3 hour session per week while doing work on another screen or on hold on the phone.
It's a shame that Minecraft on a server has ridiculous requirements, because there is a need for better servers.
It's so weird to me that Minecraft has become a "children's game". Nobody thought of it that way in the beginning, when the alpha started getting really popular on Reddit and elsewhere. That perception must've started some time after the 1.0 release, in 2012.
Nothing about the game changed to make it more kid-friendly. That's just the culture that developed around it.