it may seem weird that there is a girl and 20 years old.
Statistics show that "45% of gamers are female (up from 42% in 2012) and are usually over 18"
SourceSo no, you will never be the only girl, not even in Blockland.
Plus there are plenty of adult Blockland gamers, I myself am 22 and 2 of my IRL friends that play Blockland are 23 and 24.
Sure, there are a lot of prepubescent children on here. But because of the modding nature of this game, it also attracts older players.
It's not just some game where you play with Lego online.
I see it more as a game-design engine with 3D and internet multiplayer build in.