The cookie banner should have a "refuse all" or, to be more accurate, "accept only essential cookies" or "refuse non-essential cookies" or "[insert a label here]" button.
It has an "accept all" button. It is only sensible to have its opposite button.
Although the same can be achieved by going through "customize settings", it takes extra clicks and time to reject all cookies, so that not having that button is (intentionally or not) a dark pattern that induces visitors to click the button which will most swiftly dismiss the annoying banner.
Made with GIMP.