They can refuse to serve you, however, they can't then turn around and claim that those who clicked "I consent" actually did freely opt-in to tracking because they genuinely wanted to be tracked - because, obviously, they most likely did not.

In essence, GDPR states that you're not allowed to violate the privacy of people unless they really want to (freely given, informed, narrow/specific opt-in consent) - and this time, all the oft-used loopholes to "extract consent" don't really fulfil the criteria, as forced consent is not considered consent.