Well it shouldn't be.
If the senior players are allowed to miss open nets & give the ball away without being written off as not good enough, in the assumption they will get better, the kids should have the same leeway, it's far more difficult for them, than it is the seniors, who are used to playing that level.
There is no reason why a kid should be judged more harshly than seasoned pros & indeed that was never the case in the past, it was the opposite, & kids were allowed more leeway to make mistakes, without it being assumed that meant they would always make them.
If Jesus had been an academy kid the same age, his pre season finishing would have him written off, on here.