Earlier quoted context omitted.
>Why don't they just unilaterally disable third-party cookies by default without providing any replacement? It's explained in the article, and below in this thread. They legally cannot due to intervention from the CMA.
That's not what the article says. The CMA is intervening based on their plan of replacing cookies with Topics (née FLoC). If they just wanted to drop 3p cookies without a replacement, they could.
That's debatable, but I doubt that's the case. The CMA isn't a privacy organization; they deal with monopolies. They're intervening at the behest of other advertisers who are concerned that they'll lose the ability to adequately track users under the Privacy Sandbox proposal. The CMA's chief concern is that everybody is on equal footing.
The alternatives proposed for more private ad targeting have gone through multiple evolutions, including FLoC and Topics, but these were created largely in response to the CMA's objections.