Losing to a team that is not well known at all is of course very embarrassing for a big team like Manchester United at the moment, even though the match was only a pre-season match, but Manchester United should not have lost although fielding young players and most of the second tier players, previously Manchester is actually the favorite able to win over Rosenborg but in fact their lost from a team level is far below Manchester United So far, the pre-season match has been used as a match to test the strategy and mentality of young players, but the defeat against Rosenborg clearly shows that Ten Hag strategy is not very good, although the defeat against We can't use Rosenborg as a reference if Manchester United is still in a bad condition at the moment, but I think it's better for us to judge Manchester when they play an official match against Manchester City at the Community Shield later.
To be fair they were 4th in their group behind Copenhagen and Galatasaray last season at UCL, so that was embarrassing for them as well and wasn't even a friendly, we are talking about UCL, and they spent more on a summer than those teams worth, so it's really shameful that they couldn't build a better team. On the other hand, I agree that friendlies doesn't matter, we can't really see the situation changing anytime soon, and we will end up with something that will take a while.
In the end, we should see how things will move on, and I am sure that we are going to see how things could change as well, meaning that we are going to end up with a much better result one way or another. If we can make that work, then we are going to end up with United having a better season.
ETH is not the only issue, how that team was managed could be considered as their issue, but nowadays they are improving that, looking at latest transfers and rumours, I can see the improvement they are having. This should definitely be something that may take some time, but it will not be all that simple to achieve in a summer, it may take a few seasons but if they keep this up, they can be one of the best teams in the league.