After all, so far under Mikel Arteta's tutelage, Arsenal has focused more on its Domestic League than the Champions League. That doesn't mean they don't want trophies in this competition, but in order to remain consistent on the right track Arsenal chose to focus on their Domestic League competition. Apart from that, the competitors in the Champions League are very diverse with the depth of their respective teams. So, to stay on the right track, that's why Arteta doesn't focus too much on the UCL competition.
I have this feeling that Arsenal as a club have developed this fear against champions league which have made them lose whenever they try to compete for the trophy. Usually, they tend to work hard to get to the qualifiers and to the point of round of 16 then there comes this breeze that blows off their chances to win. If clubs like Dortmund who have taken the trophy in the past will strive their way to take the trophy again thereby getting to the finals, I see no reason why Arsenal cannot get there too. I also don't see this as a Mikel Arteta factor either.