Arsenal should be able to compete in the two competitions and they can't choose one of the two competitions for them to focus on because after all they are very prestigious competitions and worth fighting for, Arsenal last season appeared very superior and even they were able to become a team that is serious enough to challenge Manchester City in the championship competition in premier league, not only in the league, Many of us actually hope that Arsenal can achieve great achievements in the Champions League last season considering their squad which had a pretty good performance but again and again Munich is a stumbling block that continues to thwart Arsenal in the Champions League, currently Arsenal must indeed be able to get the Premier League trophy to restore the mentality and also the confidence of their squad,But isn't it also better for Arsenal to continue to fight in the Champions League and who knows if they are lucky next season they can get one of the two trophies at the end season, but what is certain is that at this time Arsenal must be able to develop their squad to be better by bringing in experienced players to improve the quality and mentality of the team next season.
Even if Arsenal focused only on the Champions league I doubt if they can actually win it, Arsenal are strong team currently but in the UEFA they are still behind especially in mentality compared to big teams. Barcelona even sadly failed in this last season when they shifted their focused to the champions league since it was clear to them they didn`t have much hope for their domestic league, mentality has a huge role to play here.
Also I don`t think Arsenal squad really lacks experience or trophy mentality since many of them have won top trophies from their previous clubs rather the entire team lack mentality for consistency when it`s obvious that they have everything to function well.