Well according to the narrative of Craig of the Creek. Each group of kids have their own theme that separates them from the rest. like the paintball kids, the scouts, ninjas, and maybe even more as the show goes on. Then you have the teenagers who are also part of the creek. They just happen to be very much into DnD, so like the rest of the kids, they too have their own attire, which is dressing up as their characters.
I think you might be drawing too much from real life, and possibly this website
if you see someone dress up in a cartoon and immediately think its supposed to represent something negative. Out of all the episodes so far, the DnD group hasnt been presented in a negative light yet. At the end of the day, theyre just another group of the creek