Actually Sevilla have tried many times to qualify for a better phase in the champions league but fate had other plans and in the end they were much more successful in the European league. I think it's not a matter of readiness or lack of belief in the Champions League competition, it's just that when a team has fought hard but the results are still empty, then they have to get options that allow them to at least win titles every season and competitions that are suitable for Sevilla for many seasons. this is the european league. Therefore every team definitely wants to get the best results, but as long as the team is able to compete in the competition they are good at, it's not a problem.
There were YEARS when they won the europa cup and went to UCL and during group stages became third and went back to Europa and won it again. Think about how great you need to be at europa that you WIN it, and then go to ucl and then lose there and come back to europa and you win it again.
This may have happened 2 times as well which is why I think it's quite important to realize that this team has some sort of magical boost when it comes to this league. I know that it's not going to be every single year, like I am not expecting Sevilla to win it next season, but it is true that they are magically great at this one. This is why I honestly expect them to do as well as they can whenever they are there. It's just matter of being so used to playing at this level.