There are definitely flaws in their plans, Manchester United's defense is a little weak but those of us who understand football fairly well must say their midfield and attacking line-up is very strong yet they cannot do well with this team.
It is quite likely for us to see Manchester United defense getting better. Have you heard of the most recent transfers? They have signed Mazraoui and de Ligt. They are aiming to sign a defensive midfielder also.
These are good steps to take to fix defensive problems at a big rate. Europa League winner odds aren't determined yet. But I expect Manchester United to be one of the biggest favourites of course.
It isn't unrealistic I think. It is all up to having a working system after making the right transfers. I hope ten Hag won't fail about that this time.