Ask HN: Are cookie consent banners meaningless?

A large portion of websites I visit for the first time all show a cookie consent banner. I was curious what accepting or rejecting in that banner actually does. After all, as a web developer, I'm used to seeing most cookies sent with the initial page load.

So I've started using the browser dev tools to just look over the list of cookies that are sent and stored to my browser even after selecting "Reject All" or whatever the closest option is, in the cookie consent banner.

Turns out I usually still see a flood of marketing and ad related cookies. A few sites I've reported as a bug back to the site owner, with a reponse of "thanks for surfacing this, we'll work on it.."

Curious what other people are noticing. And in general, is cookie consent a real thing, or are these consent banners just part of normal UX now and people include them without really implementing the corresponding app behaviors?