I'm a fan of Minecraft however something that is common in all creative games, it tends to become boring over time. Once you have everything in Minecraft, you lose the sense to play anymore due to your will to obtain new stuff being filled. I feel if you want to extend your interest in Minecraft, it helps to develop ideas for large scale projects. Also on the topic of Minecraft being childish, it is far from childish. Just because alot of children enjoy the game doesn't give you any reason to quit playing. Its basically like calling an adult who plays with Legos childish, everyone plays with them but some are more advanced with it.