GDPR isn't about cookies, or any specific tech. It's a GENERAL Data Protection Regulation.

On top of that it literally defines opt-out as the default state

As for browsers, imagine if world's largest advertising and tracking company that incidentally builds world's dominant browser and dominates all web standards would implement this as a browser switch instead of inventing new ways of tricking you into surveillance? https://x.com/dmitriid/status/1908951546869498085 and https://x.com/dmitriid/status/1664682689591377923