Those popups are not only necessary for cookies but for any kind of tracking that requires consent, e.g. all tracking for purposes of advertisements. So if you do browser fingerprinting instead of setting cookies, you still need that popup.

For using FloC data, if the granularity is sufficiently coarse so that a person cannot be identified by it and no specially protected groups can be identified (i.e. sexual orientation, religion, minors, etc.), then presumably using FloC data won't need that popup. But that remains to be seen, I guess it will take a few years of discussions in court until this is settled.

3rd party !== 1st party.

Same site cookies aren't going anywhere for the foreseeable future, the vast majority of user session capability is built on the existence of cookies. 3rd party cookies only affect embedding of sites hosted on other domains, (mainly ads), which don't use cookies for user sessions but user tracking... or to use the ad industries euphemism "personalisation"

A solution that works in every browser and gives the user choice is hardly nonsense (also cookie law != GDPR). It's much, much better than a dominant ad company forcing through a solution that works in their browser and which users presumably can't opt out of.