The Europa League competition may be seen as a competition that is not meant for clubs but some times we have seen some top clubs in Europe playing in the Europa League competition when they fail to qualify in the champions League as a result of not finishing among the 1st four teams in their domestic league. I think seeing the Europa League as a competition for teams that could not qualify for the champions league competition is better than regarding the Europa League as a competition for small clubs because teams like Chelsea, Barcelona and Manchester United have all participated in the Europa League and they are also winners of the champions league competition.
However, the situation of each club can change in every season. You must have seen how teams that have won domestic league trophies and qualified for the Champions League finally have to struggle in the new season.
Some teams may be consistent and dominate in the Champions League, and the Europa League cannot be underestimated. They still contain strong teams after the competition.