Manchester United should be among the favorite team to win win the Europa League if they perform well with their new signings and if Ten Hag use his young players well than using all these old players he have in his squad and some overrated players.
Let’s not forget Tottenham, AS Roma, and FC Proto, they can also be among the favorites to win the Europa League because they are also not small to win the Europa League because they are also rated almost close to Manchester United.
Ten Hag must also make good use of the old players at Manchester United now, because the new players also need a little adaptation and adjustment with the other players when they are in one squad for all matches. This means that every player is useful and should not be underestimated, especially as Ten Hag himself must have great determination next season in order to win the European League trophy and also his own domestic league. However, as you said, other teams like the ones you mentioned could also be favorites to win the Europa League trophy next season because they are not weak teams either.
It's important to understand that the old players were never the problem for Manchester United, it will be unfair if the most part of the blame is pushed to them just at once because new signings are coming to probably replace them. Whenever a team is performing poorly, there are usually a number of factors leading to that,so it will not be just fine blaming all on the players alone without looking into other circumstances that may be surrounding the team. At This point because much have been said about him, it's very possible he will be determined than he was last season to getting a better performance but ten hag should still work on other things and not just buying players.