You can play with anything at any age. I think they are cool, but I personally don’t play with them. I’m also not against people that do, regardless of their age. Everyone is free to play with what they want.
For a few years (as an adult) I was buying many of the sets and putting them together and trying to do my own builds. I don't have them anymore but I'd love to get more of them, building is so relaxing, it helped with my anxiety. This post makes me want to buy another set lol