I doubt statistics won't be consider personal data. For example "Someone shot 5 shots on goal" is not exactly personal data. "Simon Munster played 54 mintues" should not be personal data it's a fact of a public event.

A famous athlete wearing a brand sneaker is also just a fact of a public event. Yet if that brand uses it in advertisement they still need to pay the athlete for permission.

No they need to pay the athlete to wear the brand. Otherwise he wears a different brand that pays him. They also pay for the time the athlete spends making ads for the brand.

If the player just wears the brand through their own choice and they company advertises "As worn by Jordan in NBA all-star game!" then they would not need to pay.

Ads and stats are two completely different things.

GDPR personal data is anything relating to an identifiable person. It’s not an expectation of privacy standard. Data gathered by observing you in public is protected the same as data you share with the controller in confidence.