The reservation thing really bothers me too, but, it's just part of living in a nice area. Here in CO, you need to book very early to get a reservation at any state park that's within a reasonable driving distance from Denver.
We got lucky this year and snagged a spot at Boyd Lake State Park in Loveland. It's not mountainy at all as it's actually in town, but it was nice to get away. We had an end spot, and we could only see one other campsite from our spot, the rest were behind us, so that was nice. My biggest issue was all the kids. We are not seniors, but we also don't have kids, nor do we want to hear kids screaming at all hours. However, that complaint is not really a camping issue, and I know kids will be kids, so we can't exactly get mad at kids screaming and playing in the mornings after 8am. The biggest "offender" was the campground host site, who had their grandkids visiting.
I always thought it'd be nice if there were "adults only" campgrounds that weren't geared to the senior crowd and weren't like RV parks, but there may not be a lot of interest in that... we're the only couple in our group of friends without kids.