Opt-out is typically covered by a ton of shady UI patterns, so it is hard to do this. Another clear violation of GDPR is punishing those who does not agree for tracking by serving them crippled content or no content at all.
And just to make it clear: I am strongly against extraterritorial laws like GDPR or FATCA. US does not have any rights to enforce their regulations outside US, similarly EU does not have any rights to tell people outside EU how their websites should look like. This is clear abuse of the economic and military power that US/EU have.
GDPR has some good points (like PII data storage rules), however some of its regulations, like the once that force open forums to provide "right to be forgotten" for posts, are pure crap.
The unfortunate vagueness of this regulation does not help either - real live example from Poland: if school teacher takes home pupils copybooks, which are signed with a pupil first and last name, does this mean that GDPR rules apply to the teacher (getting consents, proper handling and storage for copybooks, etc.)? Some lawyers claim they does not, some say they does, some have no idea. As a result in some schools pupils are forbidden to sign anything that enters the school building with a full name... Overreaction? Probably. But you never know when some mean parent would want to use GDPR against the school.