Well it depends on who that person was. If it was someone your own age they probably don't like that your different and maybe because آپ don't like the same things as them. Being mature is always good. I am told different things, that i am really life smart (I doubt that) that i'm like a little kid, and that i'm quite mature in my ways. I don't know who i am but i guess i'm a mixture of both. I am the same age as you, but it depends on what your like. If آپ are like me and just don't like it when people act like four سال olds that fine. But there is a boy in my class and he is a bit too mature sometimes, like he wont let the class have a joke and if someone does a little thing he tells on them (that could also be counted as immature) I'm rambling here but basically i'm saying if your the type of person who pretends they know everything (which i doubt آپ are) and act like peoples parents then i would say آپ could probably loosen up a bit. If آپ are just into older stuff like different music, clothes (depending on what type) and different ideas of funny then آپ are fine. Okay my ramble is finished*Everyone cheers and pushes me off stage*
It depends on the type of people آپ hang out with. If آپ hang around kids who act like they're 10, you're probably in for some trouble as their immaturity will really annoy you. However if آپ hang around people who are as mature as آپ are then آپ should be fine.
Maturity is usually a good thing. It means you're responsible and likely don't go into random outbursts for the smallest inconvenient things. Or...something along that line. Besides, judging آپ right now (since I don't know you, its not going to be completely accurate), آپ seem slightly childish. آپ use a lot of exclamation points, laughs a bit, say "btw" instead of the entire thing, and apparently typed "think" instead of "thing". I wouldn't worry about not being fun یا whatever آپ might associate maturity as bad.