Actually Arsenal should not even focus in winning the Champions league now, their main focus should be winning the EPL instead which they have a better chance of doing even Man city who have been dominating the EPL found it hard to get their first Champions League Trophy even with excellent players and a coach like Pep but with time they finally did which I think Arsenal can if they are consistent enough to snatch the EPL champions title from Man City.
You says is true that because Arsenal has failed to compete with Manchester City for race title in Premier League two season in a row and i am sure next season Arteta will give his priority for that league compared to Champion League trophy but Arteta said he will give his best in this competition and will attempts to bringing Arsenal to performing well for next season and Arteta said win Champion League is very hard target for Arsenal even the managers before him were failed to bringing Arsenal to gets trophies because we all know during their history Arsenal never gets the trophies from this competition
If talking about Arsenal performance in this competition with Arteta actually they have good progress because after always be stuck at round of 16 for 14 years finally Arsenal can able to advances to the quarterfinal last season but unfortunately Arsenal was unable go further more because on quarterfinal they were eliminated by Bayern Munich with narrow aggregate 3-2
For next season we all know Champion League will have new format and mostly the participants of this competition will do more matches compared to last season and about Arsenal performance for next season i personally still stick to my opinion although Arsenal is a big team but i didn't considers them as champion candidate but i think at least they have potention to repeat their last season achievement by advances to the quarterfinal stages again