Why don't you think the browsers can agree on replacements? Most of the major browsers have proposals for replacing some piece of advertising-related third party cookies [1][2][3].

(Disclosure: I work on ads at Google, speaking only for myself)

[1] Safari: https://github.com/privacycg/private-click-measurement

[2] Edge: https://github.com/WICG/privacy-preserving-ads/blob/main/Par...

[3] Chrome: https://www.chromium.org/Home/chromium-privacy/privacy-sandb...