GDPR is not only about the browsers , it is applied outside of tech too, would be weird for the law to define browser standards . desktop apps standards and mobile apps standards.
Developers should do their job, does w3c guys could decide how to handle this and not force politicians to decide for them.
Sure some people will click accept but some of them will know who is the actual bad guy that sends their data to 100+ third parties and what websites are respecting them or at least respect the laws.
I agree that browsers could do a better job, maybe implement a shit list, put all shitty websites there and ask you only once if you want to accept to allow this bastards to track and sell your data or if you want to open the website in a special container. Then if you decide to use the container the browsers should try to do their best to limit the tracking, maybe by blocking requests to the trackers, clearing caches often, disabling some features that could fingerprint you and if it works just disable JS.
But who knows, maybe we will have to pass laws to force the popups to use certain fonts, colors and input types because the majority of websites are evil.