I agree, and this problem is even bigger than commonly understood.
It is one thing that we know all traits of people surrounding us and can be prepared to counter them regarding political intrigues. But most people don't realize what OP mentioned, that by knowing exact martial score of every commander - you are never surprised by enemy's competence.
Imagine if enemies of Alexander , Hannibal, Genghis Khan or Khalid ibn al Walid (that's the main guy responsible for islam's expansion and utterly moping the floor with Byzantium and Sassanids despite their great superiority) knew way before the war that this country has incredible military genius as their commander. They could avoid them or 'cheat' (assasinate etc) in so many ways. We players are in this situation - without any investment in espionage you are never surprised by the quality of your enemy.
There should be some degrees of knowledge about other characters.
*Some traits should by their nature be mostly secret to everybody (homosexual) - this is already going to happen in ck3 IIRC
*Characters close to you - your family, court, realm, allies - should have most of statistics and traits uncovered entirely
*Character from neighboring or culturally/politically close realms should be not known so well without some investment in espionage (assigned individuals or entire realms)
*Characters from really far lands and cultures should be enigma with only vague display ("Known as good warrior" instead of "martial 15" and meaning scope of like "martial 10-20") until you interact with them for extended time or specificaly invest in spies and ambasadors to know them.
This could be customizable rule as well. So if you want to suffer for arrogance and be surprised by military/diplomatic genius from underdog barbaric realm - you can.