Not every player is a prodigious young talent like Mbappe, Hazard, Rooney, I won't even mention Fowler and Owen who both underachieved from a similar potential that they showed at the age of Mason.
Look at Henry at 22, completely flopping at Juventus. Lewandowski at 22? Still in Poland linked to a move to mid table Blackburn Rovers. Arjen Robben at 22? Talented cog in a brilliant Chelsea title winning team but still inconsistent. Franck Ribery at 22? Scoring only twice for a Metz team while impressing greatly. Sadio Mane at 22? Still in Austria, unknown and unproven in the top five leagues. Drogba at 22? Playing in the French Second Division. Even someone like Heung-Min Son at 22 was inconsistent at Leverkusen before improving a lot to the level he is now in his prime. I could go on for hours.