Barcelona in laliga is far better than Sevilla and if Manchester United was able to handle Barcelona in europa league that means Sevilla that has been struggling with their performance won't be tough Manchester United to defeat. I don't see Sevilla tough based on their performance this season.
Logically as you said, but sometimes logic doesn't work in football. Man United always struggle when playing against Sevilla. You have to remember in 2018 they lost in Old Trafod 1-2. They failed to advance to the UCL quarter-finals.
Maybe things are different today, but they should still be vigilant. They must not underestimate Sevilla. At least their hopes for the championship are still there, because the EPL has been very difficult to catch Arsenal.