The first question we need to answer is: what does the site use cookies for, and are those features essential?
I've populated this list based on a quick skim of the source. Feel free to edit to add more.

• _content/js/hats.js: the happiness tracking survey (hats)
• _content/js/site.js: light/dark color theme preference

AFAIK, only cookies that are used for tracking matter. For comparison, GitHub uses a bunch of cookies but also doesn't show any banners. Of your list, only the happiness tracking cookie seems relevant.

We added these cookie banners to *.go.dev for compliance with internal Google policies, specifically regarding Google Analytics. I'll check with legal again to see if their guidance has changed, but as of June 2023, their review determined that pkg.go.dev and go.dev both required these notifications.

their review determined that pkg.go.dev and go.dev both required these notifications.

As I read it, the proposal is to remove enough tracking such that the your legal compliance folks say it's okay to remove the banner and then remove the banner.

Google Analytics data helps during the site UX design and contents improvement work. Unlike github.com or other services where active users need to log in and a plenty of other loggings can be possible, there are not many alternative data sources. If there are better ways than google analytics, please share your ideas.

As I read it, the proposal is to remove enough tracking such that the your legal compliance folks say it's okay to remove the banner and then remove the banner.

Like it or not, analytics plays a part in the complicated process by which Google funds the development of Go, so it may not be quite as simple as that.

Cookieless GA4 sounds promising. I don't know how much work is involved to transition to cookieless, and if that is sufficient to remove the banners.