Campground pay rates are based on job requirements, not on your qualifications. If the work requires the skills of a teenage high school dropout, minimum wage is about all you can expect.
As one campground owner so tersely put it, "Why should I pay a workamper couple an hourly wage, give them an RV site that I could otherwise rent out, and absorb the costs of the utilities they use, when I can get a sixteen year old from town to do just as good a job, and I only have to pay them the minimum hourly wage?"
She has a point.
The caveat, though, is two-fold. Are there really teenage kids willing to work for minimum wage these days? Fast food places that I've seen advertising for help are starting their inexperience workers out at above minimum wage. And, does a teenage kid really do as good a job as an adult who lives on the premises, uses the facilities, and interacts with the other guests who use them?
If you want that campground job with site and hourly pay, it's your responsibility as a job hunter to answer her question. Why should she pay you more?
Your initial interview and/or cover letter should let her know immediately how your advanced education or experience can work for her. You need to let her know what benefits she'll get from hiring you that she wouldn't get from the other guy -- whether a teenage kid or another RVer.
Still, the campground owner may only want or need -- or be able to afford -- someone to do the very basic tasks. So, again, the pay rate comes down to this: What is required for the job?
The reality of it may simply be that you are competing with high school age kids. They're available for summer jobs. They're likely to be available for weekends and holidays. A job where they can come in and clean campground bathrooms for an hour or two in the evening may fit perfectly into their schedules. They'll work for minimum wage, without the added perks of an RV site and utilities. If they don't already have the skills for the job, they can learn them.
Campground owners may prefer more mature workers. But, if the job doesn't require your wisdom and experience, they may not be willing to pay for it.