Just a thought: I don’t know if people would complain to Disney about it. It never made sense to me to complain to a business about their customers. Employees and services yes, customers no. And if there are complaints, I think there are probably way more paying/returning cheer customers that Disney would want to cater to more than any number of complainants.
ETA: not “cater to” like “Let them do whatever they want,” more like “Let’s find a reasonable solution that makes everyone happy” rather than an absolutist approach.
They definitely do complain to Disney about it. It's not uncommon to read about people being moved to a different resort or even upgraded to a better resort/room because Cheerleader 1, 2 and 3 are chanting downs the hallways at night and it's too noisy for their kids to sleep. To be fair, cheerleaders aren't the only customers that Disney gets complaints about---but people absolutely do complain about them.
In the groups I'm in, there are only 2 types of groups that get complained about consistently. Cheerleaders and Brazilian Tour Groups (re. the chanting). I never see complaints when there are soccer tournaments, baseball tournaments, runDisney weekends...etc. People may say, "It'll be busy because it's the Princess Marathon this weekend," but it's never "Groups of unchaperoned unruly loud teenagers take over the park and make it miserable to be at."
I missed that it was HS Nationals weekend not too long ago and about hit the floor when a group of 25-30 ish cheerleaders starting chanting right next to us in the World Showcase. It was loud for me and came out of nowhere, now imagine being 8 years old with Autism, walking to Frozen and that sounding off right next to you. She screamed in pain and burst into tears.
Reality is, I spent 75 days in Disney last year, spanning every month and season, and the only ones who do the chanting, screaming, running around and excessive line cutting just happen to be the 2 groups everyone complains about.
So it's not just a 'teenager' thing...at least, not from what I've personally witnessed.