Yes, the realistic is the Europa League title, but it looks hard I think because the next opponent is Lyon. That club has better statistics than MU based when we look at how they compete in Ligue 1. Lyon is a club that has stable statistics and only lost 1 match on 5 consecutive matches, so when we compare it to MU's performance, Lyon is the favorite to get the next step. On the other side, this is the only chance for MU to repair its reputation which I think will cause some tension for the squad to strungle the win. The squad is under pressure to win the title to secure their chance to the next Champions League zone. Most likely MU will not compete on any Europa League tournament on next session.
With knock out phase, if your players perform better than opponent, your team will have good chance of winning. Recent forms between two clubs are not too important or decisive for an aggregated result in knock out phase. The biggest condition is your players must unite with each other and fight with as best as they can, with all energy they have and if luckily enough, they can be the winner.
Manchester United have crisis in this season but they still have available good elements to succeed in UEFA Europa League. Additionally, Lyon is not like a giant that can destroy Manchester United in theory and in actual matches. Chance is really opened for Manchester United in two quarter final matches with Lyon and they are able to beat this opponent.