Yes, the Europa League is for clubs that cannot get the best place in the League and they will be in the Europa League, but I don't really agree if I have to say that the Europa League is not for big clubs, it's just that maybe big clubs that are used to being in the Champions League don't feel more challenged when they have to be in the Europa League compared to the Champions League. This is a fact that occurs, although many big clubs end up being thrown into the Europa League, but the ones who become champions in the end are "ordinary" clubs.
Using the word can't get the best place in their league might sound too controversial and inappropriate. To qualify for Europa is not an easy task despite not being in the top four of their respective clubs. This is why the divide them discretely into ranking where we have the top 4 going in for Champions League and the 5 and 6th position goes for Europa so every group will have it's champion.
We all know Champions league is the big game but that doesn't mean Europa is far from the big picture. In all a a trophy is also awarded to the winner of the Europa league and we still have big stakeholders who make it a huge tournament. Every competition is unique in its own way irrespective of what made the club participate in it