I hear ya. We are a family of 4, but it seems state parks (our fav unless we can get in a national park) have "parties" as you mention. I have seen (heard actually) stereos blasting from 4 campsites away or more...and folks livin' it up till midnite. On the other hand, I've seen large groups gather 'round the campfire till midnite...and not make an issue of it as they talk within the group and not make their presence known. If you are out having fun, be respectful!
Still, we are not done yet. For us, it does allow mobility and unique experiences for our kids and dogs...while seeing the real America...national parks. So, we take the good with the bad.