To be able to win the Champions League trophy is not an easy job, let alone Arsenal, even PSG are still unable to do it. We realize that every team has the opportunity to win the Champions League trophy, including Arsenal, but it is better for them to focus on the Premier League first. In my opinion, Arsenal will have the opportunity to compete with the Champions League favorites in the future, once they are truly able to conquer the Premier League. Arsenal has shown signs of success, Arteta needs to maintain his squad performance so that it does not decline, and start next season more impressively.
So Arsenal are not capable enough to win the Champions League trophy and should focus more on the premier league? I don’t think so and if they do that they’re undermining their strength as a team. They should try and be at their best when participating in the two competitions so that they get use to it from now. If they don’t play and come out as their best in both competitions, how can they win more than one trophy in a season talk more of winning treble. I have a thing that Arsenal will win a trophy next season if they keep up with their performance or rather improve their performance, but I’m not certain which of the trophy they’ll get to win in the next season.
Actually, Arsenal has the ability to win the Champions League title, it's just that the competition is very difficult, especially since Arsenal has to face Real Madrid, Man City, Bayern Munich, Inter Milan, etc.
Meanwhile, Arsenal failed to win the Premier League title for 2 seasons and they were also eliminated in the Champions League before reaching the final. Arsenal always do their best in these 2 important competitions but cannot maintain everything at the same time if they work too hard in the end they fail to win one of the titles like last season where they focused on 2 competitions in the end they couldn't balance their performance and ultimately failed in the EPL and UCL. I agree with what @imamusna said, it would be better for Arsenal to focus on conquering the Premier League, if they feel their abilities are stronger, they can focus on 2 competitions, like Man City, who have conquered the Premier League many times, finally they are strong candidates in the UCL.