Man United have indeed had an inconsistent performance so far, but if we talk about opportunities and hopes, it would be better if Amorim focused more on the Europa League because that is the only way for them to get to the Champions League next season. So it is reasonable if Man United can win the match against Rangers because they have the reason and motivation to win the match. Now they just need to win the final match against FCSB because that way Man United will be in the top 8 and will automatically qualify for the round of 16.
That is the most realistic target that Man United could possibly achieve this season, as their chances in the Premier League are certainly very tough, as are the FA Cup (Liverpool, Chelsea, Man City and Nottingham Forest are much harder to beat than the teams in the Europa League). Their defense line is not good yet, but I think it is still better than last season, especially if Amorim is willing to give Altay Bayindir more opportunities. The biggest problem now is not the defense line, but their two strikers who are having difficulty scoring goals. If Amorim can find a solution in this January transfer window (getting a clinical striker even if he has to sell Hojlund and Zirkzee at the same time), I think winning the Europa League is a reasonable target.