The reason why English clubs have not been doing well in the Europa League is that they have been tactically good enough when going to Europe for some times now and so they got knocked out when it gets to the knockout stages of the competition, last season I can say that it was even due to luck that both Manchester United and Tottenham got to the finals this is because other teams too where not that informed
This season might be different from last season, where teams from leagues other than the Premier League weren't as competitive. However, this season seems to be different because English teams will also try to dominate the Europa League this season, although I personally have more confidence in Italian teams like AS Roma and others. I hope that in this Europa League season, one English team can reach the final, and the other will be from another league.