The last time that Manchester United won the Europa League competition they weren't playing the way they are playing now and their attacking force was far better than what we are seeing now likewise the defensive line. The team may have all the experience in the competition but it takes a team with good performance and consistency in winning matches to advance to the finals of a competition but I don't see that ability in the Manchester United team right now unless they get better.
I can't accept that Manchester United don't have a strong squad. Manchester United have spent a lot of money building their squad. However, if their squad is not strong then it is entirely the failure of the coach and management. Manchester United management spent 96 million to add Antony to the squad. Manchester United paid 75 million for Hojlund. Then the performance of the attacking players of this team is poor. Although Manchester United spent a lot of money, they failed to select the right players for their squad.
You have given a typical example to what happened last season when everyone expected Liverpool to be the favorite team to lift the Europa League trophy but we saw them being eliminated and Atalanta and Bayer Leverkusen advancing to the finals, United can win the Europa next season if they improve in performance but it is not certain because there are other good clubs in the competition.
Last season I also thought Liverpool and Leverkusen would play in the Europa League final. But Liverpool were eliminated from the Europa League after losing against Atalanta. Basically, big teams like Barcelona, Liverpool or Arsenal do not take Europa League seriously. This is why we don't see these big teams performing well in the Europa League.