Numbers just help to provide context.
Fans choose a hill and die on it sometimes. Xhaka can have 16 straight good games and 1 bad one and people will say he has always been like that. Availability of numbers writes out the idea of using emotions to judge players and more of facts.
It's okay to use the eye test to judge players but numbers are currently as important. Because fan biases mean they can forgive Guendouzi for making 7 mistakes and want the club hierarchy fired for one Xhaka mistake.
It happened with Mari and Gabriel. Gabriel needed to make around 6-7 mistakes to turn heads. Mari would just lose a pace battle and everyone would want whoever signed him fired.