It is normal for you to make such comments because Leverkusen was defeated in the UEL final, but if they had won, different comments would have been made. Leverkusen had a great season and suffered only 1 defeat in all matches. The Leverkusen coach is not inexperienced. It means he has old experience. He achieved great success in his first season. I hope next season will be better for Xabi, but I don't think it will be better than this one.
Usually people will always have a way to talking against the fact that it could have been better especially when it turns out bad and not favoring enough, it makes them have a perception that you didn't succeed enough just because you failed to meet with their expectations and thats the case with Leverkusen at the Europa this season, they had expectations people had of them but it turns out they didn't get to meet up with such expectations.
Leverkusen for me still remains a very good team and did so well this season such that not winning the Europa title will not be considered such a big deal for me because I know they are not a weak team and it was just a normal team in football to get to taste defeat at a point especially for a team that didn't get to experience defeat throughout the season, it's such a good achievement for them, if not for anything do the fact that they have been able to gather experience such that in the nearest future they will be able to do even better than they did this season.
In the bundesliga now Leverkusen is seen as a very top team and if they were to be in the Europa again next session, I'm very optimistic about their performance been a top notch performance but then they have been elevated to the champions league a d I don't know if by the new rules of the champions league they are still going to allow teams to be relegated to the Europa of which of they so then we can say if Leverkusen fails to pass the group stage, chances are they can be in the Europa again next season.