That's what the GDPR mandates already - the problem is that there's no serious enforcement of it so websites are allowed to get away with non-compliant banners.

That's what the GDPR mandates already - the problem is that there's no serious enforcement of it so websites are allowed to get away with non-compliant banners. Cookies is purely for the previous "ePrivacy Directive" (aka stupid cookie law) but nowadays you must comply with both - and complying with the GDPR will in the vast majority of cases inherently comply with the ePrivacy Directive anyway.