People about Cosplay...
Absolutely not! There are exceptions, but even seasoned cosplayers who enjoy the crafting side of things will often buy parts of their costume. There’s an entire segment of the community that does commission work who wouldn’t have any business at all without the parts of the community who find skipping to the dressing up stage to be most fulfilling.
So long as you are having a good time and participating ethically (not taking credit for a costume someone else made, for example), you are doing cosplay exactly right!
Putting aside for the moment that the tone of the question doesn’t imply the most open of minds, cosplay is – simply – acting. Do you consider Mel Gibson, Ken Branagh, David Tennant, Cumberbatch, et. al. immature for wanting to dress up and act as Hamlet? Cosplay is a similar – if not identical – mindset: people, inspired by characters, possessing the right combination of talent, bravery and self-awareness, performing as said character for an audience. Whether it’s a convention stage or a Broadway stage makes no difference. The person who portrays Deadpool or Master Chief is very much spiritual kin to the person who plays King Lear or Hamlet. It’s wrong to praise one and denigrate the other based on the source of their inspiration, for to declare which works are “great” and which are not is subjective or worse. Still, even if most consider it blasphemy to compare Marvel to Shakespeare, the motivation to portray characters from either realm is identical and the healthy mindset WON’T criticize this, realizing that whatever it doesn’t “get” is not automatically inferior or invalid.
PS: Ironically you will find, if you but ask, that most cosplayers as children were very successful Trick or Treaters, as Halloween is quite often the “bug” that bites them for their subsequent motivation.
To me, it’s equally a tribute to the property that I’m making the cosplay from, and the art form.
One could say the same thing of not getting the appeal of creating any media – learning any instrument, painting a picture, writing a book. It’s creation and display – this may not be the same to everyone, but it’s definitely a big part to me. It’s also a way to meet new friends from all walks of life. I’m certain if you looked closer, a lot don’t meet the stereotypes of an overgrown kid. I cosplay with people in the military, aerospace, tech, and all walks of life. Conversely there’s people that do this for a living, myself included.
As someone that enjoys hobbies and media that was formerly shunned for being “too nerdy”, perhaps immediately throwing anyone that takes part in cosplay into the “you’re a man/woman child” box is a bit reductionist, and a little offensive.