Age or experience doesn't make you a leader. It's an aspect of your personality, some people are leaders, some people aren't.
He was never given the armband by any manager properly during his prime, only once literally every hint of leadership had evaporated from the squad.
He's been an absolutely phenomenal footballer for this club and is genuinely one of the best strikers in the history of the Premier League. He's a handful of goals off the all time top 10 ever and he's done it for Leicester ****ing City.
He just isn't particularly much of a leader and that's fine. He's plenty of other things. Our current plight is not his fault.