It's pretty hyperbolic to call Google results a "full page ad". For example, if I do a Google search for "clickbait", on mobile all I see above the fold is a dictionary definition stub followed by a wikipedia snippet. There is actually no sponsored content at all. Even scrolling doesn't turn up any ads.
And yes, of course, there are other types of searches where the first thing you'll see is shopping results, followed by more sponsored results. And yes I hate it as much as everyone else.
But I don't think it's reasonable to say it's an "ad engine".
The amount of real estate devoted to monetization has been increasingly silly for years. It will no doubt get worse. They do have an effective monopoly. It sucks for the internet that this is the case.
But Google is still an impressive search engine underneath all the monetization. One where a huge part of the mindshare at the company is still devoted to organic search. I don't think HN is a place where you can reasonably hope to get away with claiming otherwise.