I don't know if this was the OP's first state park experience, but if so, I hope they'll do some review checking of other state parks, and give it another try elsewhere. There are some really nice ones out there...
Then again, if the OP's experience was typical of all Maine State Parks, and I really hope not, I'll take a visit there off my bucket list. We've stayed in east coast state parks from Florida to upstate NY, usually on spacious sites often with foliage separating them from the next site. Sure we've had some noisy neighbors at times, particularly those with young kids, but they've always settled down by quiet time or shortly after. Maybe we've just been lucky all these years, but we even chose a NY state park for the 4th of July week, specifically because they do not allow fireworks, and they do enforce it.