My experience is that most people assigned with boring, repetitive jobs will either automate some of it or start cutting corners to avoid the work.
(In fact I'm starting to believe that the first runaway evil AI trying to take over the world will get stopped in its tracks, because it will not understand just how different the "on-paper" states of inventory and books in small and medium businesses are from reality.)
Your solution is to say they all provide value?
The intern's requirements in this job are not "press every link presented" they are "find out who is not providing value for their worth" however the press dgaf about that.
The above is not advanced management techniques, it's basic check work.
You'll find all sorts of personalization opportunities and you get to cut out the middle-man.
The point I intended to make is that, in my experience, there aren't site owners going "I wish I could do this if only it wasn't so technically hard", they're going "I wish I could do this if only it didn't mean people would spend less money with me". Because on the other side of the equation, ad buyers (generally, though obviously not universally) don't want to work that way, and they're the ones with the money and therefore the power.
I'm not a developer myself but I've worked with developers who created various in-house ad-tech, and while this sort of thing may be too complicated to do for Mr Random Joe Blogger without a CMS plugin, it's really not something that is too technically complicated to be feasible.
You could always contact a single magazine, but big corporations would let their ad agency handle distribution
Billing is a solved problem too, no?
No. Billing is a huge pain in the ass. Negotiating price with each site is a huge pain in the ass. Building a reliable JS snippet that works everywhere and that these sites will trust is also a huge pain in the ass. Everything about dealing with 5k sites manually is a pain in the ass, which is why ad networks exist in the first place.