I think most cookie blockers work not by accepting everything, but removing the popup/banner out of the way - but like @gp says, this is sometimes tricky. I maintain one such blocker of my own for Safari, but this is something definitely non-trivial and something that needs to be sometimes updated and not a one-off. There are different kinds of banners, some can be harmlessly hidden, sometimes you'd also need to re-enable scrolling, or remove blur, or other things like that, and sometimes there's nothing you can do. And sometimes it happens that a site changes something at some point - e.g. hiding a div was earlier enough but now it also started blocking scrolling, or added an overlay below that wasn't there before, and the site ends up in a broken state.
Not to mention that there are literally thousands of different class/id names used, with a large "long tail"… so you'd need some kind of machine learning to detect the banners probably 
So I'd say this sadly isn't something that can be handled in a general way on the browser side without maintaining a blocklist or referring to someone else's - at least until maybe one day someone comes up with some general protocol that can be used for this and all sites implement it…
