Looking at this strictly from the point of view of the user, WiFi is one of the amenities advertised by the campground. If your site doesn't get WiFi they have not provided what they advertised.
If someone parks an airstream between you and the source which prevents you getting WiFi at yor site, then they have failed to provide the service they advertised. An inadequate layout of the WiFi system isn't the users problem. It would be like providing a water hookup which was only a trickle and then saying that they can't help it because too many users are showering.
Maybe when you call them for reservations or check in you should ask them about the actaul WiFi quality and availability. They should be honest(and I believe most would be) about the WiFi and maybe offer a site to you which is likely to have good WiFi.
I do sympathize with campgrounds as most of the older, small ones are probably not making a large amount of money and can't spend too much on WiFi upgrades. Some of them are in the process of upgrading old electrical systems to accommodate todays Rvs which use a lot more electricity than 30-40 years ago.
I agree that not allowing streaming video downloads is reasonable. Unfortunately the honor system works best and some people feel since they likely won't get caught doing this they don't have aproblem with it.
Steve