Real question. Is minecraft for kids 8-15 years of age or am I missing the point of it?
Only people I have met playing it where kids.
Wrong. Actually it has become that, but previously it was not. A few years back Minecraft was full of young adults, and it was very fun to play and collaborate with people on various projects. However, as it grew popular it became attracted by millions of kids worldwide and the community is naturally messed up (similar to League of Legends). Even though many think this game is easy, try building
Minas Tirith in survival and then we can talk. This was just a example though.
I actually deleted my Minecraft account over half a year ago (yes, permanently closed). I have no idea how adults find time for such games? Maybe being lazy after finishing education (e.g. working after college, and no further education) is a mainstream thing. Anyways, good luck with your server OP.