They may have lost to Rosenborg, but if you look at the match statistics, Manchester United could not show any presence. Rosenborg found 22 positions, while Manchester United found only 5 positions. Manchester United has been playing mediocre in the pre-season. If these games continue this year, we will probably see Ten Hag dismissed from the team before the end of the season.
Hopefully Man United won't play that bad when the season starts. And actually in the pre-season match against Rosenborg we saw that Man United did not play with their best squad completely because in that match Man United also gave the young players the opportunity to play. So I really understand these results. But if ten Hag is able to make a good strategy then even with young players he should be able to show a better game than that.
But in reality he has not been able to make the club's performance in its best condition. But I think we are too early to judge because this is only pre-season and even player transfers have not yet been completed. We'll see when Man United's main squad is there, namely when the transfer market closes and the season starts. But if in the next pre-season match Man United still doesn't show good results, it is very natural that many will be pessimistic about Man United's performance when the season starts.