Fullbacks, especially those high energy ones who really on athleticism peak quite early. Robertson is not good enough on the ball to adapt his game and he's not as good a defender as Tierney. And ge
The signs have been there for a while. He made two goal-costing errors in qualifying (Belarus and Denmark) and his bad pass, which was never on, heavily contributed to Brazil's second goal.
I'm not saying he shouldn't be in contention but he shouldn't be an automatic first choice.