A couple things: While this probably looks different from an end-user perspective than Google's earlier moves to refine the browsing experience, from an advertiser/publisher perspective it's the same old game. They killed private blog networks in 2014 and while you saw an incremental improvement in search results, SEO companies got fuckin' scuttled. (Note that the site linked employs just about everything Google intends to kill) In 2015 Google informed the world that if their websites weren't mobile-friendly, they'd be pushed to the bottom of the search results. Everyone scrambled again but since this wasn't seen as a direct shot-across-the-bow to advertisers, people panicked less. It required just as much work to fix, though. And realistically speaking? Facebook has built a silo for a very good reason: they don't want to be beholden to Google. Apple silos everything in Safari for the same reason. Pinterest does such a good job of screwing up Google image search results you'd think it was deliberate. And from our web traffic, we're about 30% leads from Facebook ads, 50% from organic search (20% from driving by the damn clinic - good thing we have such great street traffic counts!). Google is basically deciding they're no longer satisfied to just give you the road map and hope you look at the ads every other page. They're going to become the highway authority. Let's be honest - anybody who has used the web for more than a couple years already sees right through that advertising as if it weren't there. I've been bannerblind for fifteen years now. The standards they are likely to impose are all those things that drive people to install AdBlock in the first place. The goal, clearly, is to be not quite annoying enough to cut it all out from the get-go.
Most of the fear about this new development - which has lots of precedent as you point out - comes from the media outlets for whom this is another nail in their coffin. Maybe you're agreeing with me on this (it's not entirely clear to me), but I think Google becoming the highway patrol means they've crossed a line not yet crossed before, one that I think will give them enough power that they probably can't resist using it on their ad competitors. I worry that the reverberations will be felt in many more places than just at media companies that should've been dead already - if your 30% suddenly became 18%, I think you'd notice. I'd actually love to know what ad agencies think of this, especially since you posted a while ago about how they hate how online (video) ads are organized these days.
Thing of it is, if your news isn't in an app wrapper by now, you're already dead. NYT. WaPo. Chicago Tribune. LA Times. Albuquerque Journal. Yeah, it's a line not yet crossed but if you're still out on the field instead of in the silo you already missed the harvest. The Do-Not-Call list had a seismic effect on telemarketers but nobody cared that much because everyone hated them. Unconstitutional? mos def. But it still happened and nobody mourned. Banner ads are gonna be the same way. How do marketers feel? If they had any faith in CPM they wouldn't have thrown all their efforts into viral advertising.