One of the problems with developing an app or site that includes everything is that there are so many "must haves", often each different for each individual. Finding a way to provide links to the different "most haves" without making the site too cumbersome is the trick.
For example, AllStays link to a Google search for campground reviews worked well in the past, however I've noticed that the rvparkreviews.com link is moving lower & lower in the search results. A direct link would probably be more useful...
I think AllStays (and the others that use filters) provides a useful interface, however if you added Maps, Satellite views, local attractions, and some of the other suggestions, I suspect it would become more difficult to use.