Foden is 22 and has five league titles. Haaland is 22 and has one plus playing in a new league along with Alvarez who is 23 and is a world cup winner. Rico Lewis arguably turned our season around and is 18. Dias was 23 when he joined City and has won the league in every season he has been here. Ederson, Stones, Raheem, Zinchenko, Laporte, Jesus all early twenties when joining City and all league winners.
The big problem with waiting for players to grow up and mature is that they either get bought by other teams that are winning stuff, their form collapses or they don't actually improve. They don't get replaced by better players and like Spurs the squad gets filled up with rubbish. Incremental improvement is one of the biggest myths in football. You make giant leaps or you fall behind. If you're not going to sign players that potentially bench Saka, Martinelli, Odegaard or Saliba you're not going to improve enough.
For context before anyone argues that our young players come into a team used to winning so the comparison is unfair - in 2012 Aguero was 23, Balotelli 20, Joe Hart 24, Micah 23, Nasri 24.