He seems to entirely overlook native advertising. I know of a couple of decent sized businesses ($50mm+ annual revenue) that depend almost entirely on native advertising, because Google/Facebook ads in their niches are highly competitive, and tend to not be ROI positive. Certain niches on Google and Facebook are dominated by startups that are willing and able to lose investor money on negative ROI ads in pursuit of growth. They drive the bids up, and this creates a situation where existing companies and startups that are not flush with investor cash must look elsewhere for advertising that is profitable.
Further, Google and Facebook have an insane number of rules about how and what companies can advertise, and therefore there are billions of ad dollars that do not and will not ever enter into their coffers. These are not just in scammy niches either...you’d be amazed at many of the ads that get rejected by Facebook and Google. This pushes additional billions in ad money outside of their ecosystems.
As long as investors are willing to fund losing ad campaigns, and Google and Facebook keep increasing the number and breadth of rules that result in an ever increasing volume of ad rejections, there will be publishers and alternative ad networks that can enjoy vast amounts of revenue that gets pushed to the fringes by these forces. They just have to position themselves properly.