I don't want to comment on GDPR, but you must be kidding with 'can just block'. Do you expect that average joe can do that ? It like saying, we don't need police you can simply defend your self.
Everything comes at a price. I don't expect every average Joe to be tech savvy to use extensions. Though when visiting a site (an action that a personal deliberately takes) if they really care about their privacy on web, cookies, GA tracking they aren't probably average Joe and can use a blocker.
You are conflating "technically savvy" and "doesn't want to be spied on". I understand that these probably correlate in your world, but a simple moment to think about why most people click "no" to the iOS tracking opt-in prompts explains that these are orthogonal issues.