What killed the third-party cookie?

[fisherinjurylaw]

As per the chatter going on in Webmasters community, what do you think about third-party cookieds? Are they really dead? If yes, what killed them?

[HeavenlyBorn]

Both ITP and ETP are able to block third-party cookies by preventing them from being stored in the browser, and, to close the loophole exploited by advertisers, they can also prevent third-party cookies from being recorded as first-party cookies.