Sevilla won the Europa League this season and they were lucky enough to win this title but on the other hand, Sevilla have taken the final automatic place for the next champions league and they should get themself ready for the champions league where they are going to have harder games than what they had in Europa League. Sevilla couldn't have a good performance in most of the games in the Europa League and in La Liga but they should start hiring better players if they want to achieve something in the champions league.
The Champions League will be more difficult than the European League, which requires Sevilla to prepare as well as possible so they don't become a team that only complements the Champions League. They are a strong team in the Europa League, many even say they are the kings of the Europa League. They should be more motivated to become a team that is not only called strong in the European League, but also in the Champions League.
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.