Also I think in Gemini there's not much advertisers can do to "try to bypass these countermeasures".

They could add Gemini support in Firefox. Or even roll out their own "small web"-style protocol for hypertext. Simply without the functionality advertisers use.

With their resources it'd be a minor feature.

The issue is that while somewhere they have some people actually making a browser, as an entity it's a company making money on advertising. People deciding on directions use that as the main criterion.