Re: "it doesn't have the unquestionable dominance that it does in Search"
"Do you believe they come just from the Search Page and YouTube?"
No, not just from the search page and YouTube. I do believe that they are worth more to Google. The proportion of people that click the paid search ads is at least two orders of magnitude higher than display in my experience. Bear in mind that Paid search and Google Shopping are much much easier to make relevant for the search due to systems like dynamic keyword insertion and inventory management tools than display ads, even remarketing display ads. Also consider that if you're searching to buy something, there are potentially over ten paid links taking up the most valuable screen real estate above the fold.
And yes, in absolute terms, Google will lose more revenue from adblockers than other providers. In relative terms, they are propped up by the unaffected channels.