I was at Mozilla when this was implemented. It was completely optional for websites to support this. A few did at first. A lot of people internally wanted it to be on-by-default, but the argument was that if it was, nobody would respect it – after all, what tracking platform would willingly only track the 0.1% of people who went into the settings to enable it? (Internet Explorer did eventually enable it by default, w…
They are, in a roundabout way. Hop into your uBlock Origin settings and enable the Cookie Banners and Annoyances filters. The modal gets silently nuked in the background and you can carry on with your browsing. Since you never consented, this ought to be functionally the same as Declining the banner.
The Kill Sticky bookmark works similarly, for crappy browsers that don't support uBlock Origin (eg iOS, Chrome for Android): https://www.smokingonabike.com/2024/01/20/take-back-your-web...
(Remember when web browsers used to treat their users first and implemented things like Popup Blocking, enabled by default? I miss those days.)