According to GDPR it’s illegal to condition content on tracking approval. This is VERY clear if you read the law. I can’t understand why this has become very popular to do just recently.
In theory someone could directly sue some company which engages on this via Article 79, but this can be expensive and depending on jurisdiction the plaintiff can end up with personal liability on defendant's legal costs if court ends up finding that this is actually legal (e.g. Finland has "loser pays" rule in civil suits).
Additionally this does also touch ePD and in some countries there might be different agency which handles ePD complaints compared to GDPR, like in Finland Data Protection Ombudsman handles GDPR, but Transport and Communications Agency (Traficom) handles ePD. If there is something that touches both the Ombudsman usually lets Traficom take care of ePD aspects before they give any GDPR ruling. Both of these can take years.