It's trivial to make a site that doesn't need a cookie banner: don't set any cookies. Modern web devs have probably forgotten, but this is actually the default behavior. Cookies don't get set unless you do something to make it happen.
And cookies that you actually need for functionality don't need a banner either. If you're setting a session cookie for logged in users so they stay logged in when navigating between pages, you don't need one.
Why, then, does practically every site in existence now have one? Because they set unnecessary cookies. Because they choose to set unnecessary cookies in order to track you for purposes that are not necessary to the actual functionality of the site.
Every single cookie banner you see is a big sign that says, "We value our ability to track you for marketing purposes more than we value your time."
Apparently they're willing to say that. I still see it as a win. No tracking and no banners would be ideal, but at least the regulation forces them to be honest and up front about what they're doing. I'd rather have tracking and cookie banners announcing it than tracking with zero indication of tracking.