I don't know why you mentioned Juventus in your comment, is it for trophy purpose? Juventus club in this season is not in good form and the management of it is not also helping matters so I don't tip them to be contenders of any title starting from the Italian local League to the European level. They have to put their differences in order and get a new coach if possible in order to be able to contend for any trophy. Europa League this season has big names in it so there is no chance for Juventus.
I agree with you that Juventus this season cannot be said to be a strong challenger in the Europa League this season. The situation that is happening at juventus right now is very big because their board resigned in the last few days which makes this situation will affect the juventus squad because the mentality of the players will be affected by this condition. But juventus can solve this problem quickly before the league resumes after the world cup.
Arsenal and Manchester United are more likely to be teams that have the chance to reach the final point in the Europa League because the squads of these two teams seem to have pretty good formalities in the previous round. even barcelona i'm sure will have a tough road in europa league.