Indeed.
Don't think it is much of a problem either. Generally speaking the group stage games are a walk in the park for any PL/La Liga/Serie A side. Most teams are League One quality at that stage. Later on, yes playing in Europa League quarter/semi finals could have negative impact on league...
Europa League is very entertaining, usually with a lot of goals. Brighton would also be a top 5 favorite to win it, which would probably be the easiest way to win a competition (and also the easiest way to get into the Champions League, which would change everything).