For example Arsenal, they will also be very busy maintaining their position in the Premier League. Manchester United are busy trying to get into the top 4. Juventus are busy trying to stay in the top 4 and all the teams competing in the Europa League have other competitions that are just as busy. So it's not only about Barcelona.
you are right The teams competing for the title in the Europa League this season are all looking to do well in their respective leagues. Barcelona and Arsenal are aiming for the league title. On the other hand, Juventus and Manchester United continue to fight for Champions League qualification. So the Europa League is probably the second priority for all the teams. And so it cannot be said for sure how the teams will perform in the Europa League.
We cannot say that Europa is not a major priority for some big clubs.
Using Manchester United as an example, you will understand that Manchester United is trying their best to get into the top four of the English Premier League in order to be able to feature in the next Champions League.
But the battle in the Premier League is so hot that Manchester United need to shift their attention to Europa in order to have double chance to come to the Champions League next season. Either as top 4 in EPL or champions of Europa