Bring advertising in-house. Its not 1997 anymore, there is no reason to rely on 3rd party platforms for advertising. Everyone knows the internet is a thing now
How do advertisers know which particular sites are "a thing", especially smaller sites that are too big to be run as a pure hobby but not yet big enough to be household names?
and wants to advertise on it.
But without an intermediary, you can't advertise on "the internet". Instead, you would have to advertise on individual publishers' sites, which is much more time-consuming for both advertisers and publishers.*
Say you have 30 publishers, each of which wants to find relevant advertisers, and 30 advertisers, each of which wants to find relevant publishers. If there is an intermediary, this means 60 contracts to review and sign. If there is no intermediary, there are 900. How does a change from O(n) with an intermediary to O(n^2) without one improve the market?
And even then, how will an individual publisher be able to reassure its advertisers that view and click statistics are accurate and not inflated? All other things being equal, an intermediary such as Google is considered more trustworthy because it has more to lose should a claim of fraud end up substantiated.
* In the advertising market, a "publisher" is the operator of a site that carriers ads.