Still a stupid idea
I work in ad tech. 3rd-party cookies definitely help us in many ways.
But also, non-Chrome browsers have already blocked 3rd-party cookies for years, and we've been just dealing with the lack of those signals, fine.
The amount of effort that Google is putting into "ok we're going to remove 3rd-party cookies but also kinda come up with a weird bundle of replacements which are shitty versions of what we think people want 3rd-party cookies for and also rework how RTB auctions work in Chrome" is just suspicious.
If they actually cared about privacy+tracking they'd just say "we're gonna do like Safari and just disallow that" and then everyone would have to deal with Chrome as we deal with Safari. Instead there's this opaque system, controlled by Google, which they pinky-swear has no backdoors or other ways for Google to get to keep all of your info.
I really, really can't buy the idea that this isn't a subtle land grab by Google that they're trying to sneak by regulators. Just say "no one gets 3rd-party cookies" and be done with it.