I use the "I don't care about cookies" browser extension with "Cookie AutoDelete". Cookies are managed client-side, those banners are redundant. The purpose of open standards is that you can have a user-agent that does whatever you want it to do, so take advantage of that.

Cookie banners are the dictionary definition of a meme. They give the site makers a piece of mind, helping them sleep better at night, even if they may have no other practical purpose. Other site makers see them and reproduce them because it gives them the same piece of mind, exposing the banners to more site makers. Obviously, there are better ways to get a piece of mind as webmaster, but you'd need first to explain the problem to a lot of people before anything changes.