A pretty good debut for Mount. The 2-0 win certainly made Man United happy because many young players were displayed by Ten Hag. Although Mount didn't score, he played pretty well. Although he only played 45 minutes, he was able to immediately adapt to Man United's style of play. Although Leeds is not a strong team, but Man United at least have the opportunity to try some young players. This result does not illustrate the strength of Man United, they still do not play in full team condition.
It is pre season match and Man United didn't play against a big team. So, we can understand if Ten Hag gave more opportunities for young players. Man United doesn't need to force their main squad to play. However, I was still surprised that Varane and Martinez became the starters. Leeds United didn't put their main squad, too. I think it is better to put Maguire and Lindelof as the starters. 
Regarding Mount, it was enough for him to play 45 minutes. Sure, he played quite well although he didn't contribute significantly for Man United. He needs more time to adapt with Man United tactics and the characteristics of all players.
It is called friendly match because it is meant to be friendly between players and as such, aggressiveness and try so hard wouldn't matter to players, I don't think the friendly match mean something to rate the team or individual efforts and performance, it's just a regular match that if you observed, almost all the players were substituted so that many of them could have chance to display their presence in the match. Until the beginning of the season before we can something valuable about the players and their potential and that's how we are going to know if the amount are well spent on this young players.