I know that is what most persons will say, that Manchester united played weaker team which is not true because if we say they are weaker team or club, the question now will or should be how did those team or club manage to qualify for the Europa league? And those who are calling those team Manchester united beat weaker team, if actually they are weaker would they have qualify for Europa league off course they would not have.
Anyone who watch Manchester united against FCSB will testify that Manchester united posses them till the end of the match just that Manchester united was kind of unfortunate to score in the first half, FCSB was only playing counter game. This is the second or third time Rubin Amorim is keeping clean sheet I think that is progress, I wish he build Manchester united back again though it is going to take a season to fully achieve that.
I also think that Manchester United are playing as a weak team, you see and observe their performances, then you may correctly understand that they are not a very strong team at present. Manchester United are currently playing in two leagues, the two league are the UEFA Europa League and the other is the Premier League. As you commented that most people say that the weakest team of Manchester United may have made the same comment according to their performance in the Premier League.
Those who watched the match, that is, Manchester United, who faced FCSB in the match that the match could easily guess that Manchester United were very strong in that match. But how long has Manchester United Crystal Palace a very weak performance.