IANAL. It's not about cookies per se, it's about your information and what it's used for. If your information (e.g. a unique ID) is used for something you want (e.g. login), that's fine. If they want to use your information (could be the very same information, i.e. your unique ID / user profile) to track you, advertise to you, sell your profile to advertisers, ... they need extra consent for that.

Just in case they get sued.

..while their ads preference dialogue has pre-checked options which is clear violation of GDPR...