Under your theory, it therefore cannot be claimed as a fact that Karim Benzema was fantastic against PSG yesterday, despite the fact that he scored a hat trick, including the match winner.
Facts aren't mere statements that can be adjudicated by scientific measurement. When it is universally agreed that a footballer put in a fantastic performance, it becomes a fact by definition that that player put in a fantastic performance. Let's use an easy example: Bastian Schweinsteiger in the World Cup Final in 2014. Schweinsteiger won global accolades for his performance in that WC final. I don't know a single human being who has ever question that he was, well, fantastic in that match. But if we were to adhere to your theory of what a fact is, we would all have to deny that it's a fact that he was fantastic in that WC final. And that would be fecking stupid.
Donny is no Bastian and never will be, but Donny enjoyed widespread acclaim for his fantastic performances under Ten Hag at Ajax. That's a fact. Is it possible that everyone who watched him play is wrong and that he was actually shit or at best mediocre? Sure, it's possible. But hardly likely.
In your attempt to apply a strict epistemological definition of what a fact really is, you're opening up a can of worms that questions our ability as human beings to grasp reality as we confront it. What I am telling you is that it is a graspable reality that Donny was in fact fantastic under Ten Hag at Ajax. It is reasonable tp argue that everyone who holds this view is wrong, but in a situation where the overwhelming consensus holds A and the extreme minority holds B, the burden is on the extreme minority to prove why the overwhelming majority is wrong and not on the overwhelming majority to prove the minority is wrong.
There must have been a reason why Real Madid were interested in Manchester United eventually acquired Donny Van De Beek. It cannot be that Donny was widely held to be a mediocre footballer. There must have been a perception that Donny was worthy of playing for two of the biggest football clubs on the planet. As to why it didn't work out at United is a matter of speculation, but it is a matter of fact that Donny was fantastic under Ten Hag at Ajax.