He gave up before he ever tried. That's not endearing. And people try to hand wave it away by saying "Well he would have failed or got turned away" which is probably an accurate statement but it's beside the point. The hero needs to TRY and you need to show him failing or getting rejected for his sorrow and rise to have any meaning. It's not about actually succeeding on your first go. Trying shows conviction and strength of character. Steve Rogers trying multiple times to enlist shows his determination. Deku had a dream he didn't even want to try for and it's written off as life being unfair so nothing is his responsibility. He only wanted to be a hero if he could be the best hero and when that wasn't an option he didn't try to be his best hero he gave up. This is dreadful character building. He's a spoiled sissy who quits when it was too hard and only tried after he was promised the shiny. Captain America didn't enlist because he was promises the super soldier serum. He enlisted and struggled because he believed it was the right thing to do and was rewarded because he had true strenght of character. Deku should have been more like Steve Rogers.