At the age of 21, 22…basically a player has already established most of his skills… Shooting, passing, crossing, tackling, dribbling, and goal keeping.
As his career moves on his vision, timing, decision making will improve also.
A veteran may have most some speed, strength and stamina, but the experience compensates.
I have asked several times on this site… If there is any famous footballer that had shit/not well developed skills at the age of 21, 22, but suddenly improve significantly at 25, 26 or after???
If your skills are not good at 21, basically you are who you are for the rest of your career.