Arteta lacks the talent to coach Arsenal in the Champions League because the UCL is different from other leagues. You must focus and see how you can make information in the games because that is the main reason why many clubs do not win matches; they do not know the actual players that they can put in and win games for.
Arteta is a talented coach and he is a first coach can help Arsenal go far like the past season after many years. Is his talent enough to help Arsenal win Champions League, it's big question but there is time for Arteta and Arsenal to improve. He is still a very young coach and can improve a lot and win titles with Arsenal or other clubs in future. If Tuchel can win Champions League with Chelsea, it's unfair to say Arteta can not win it with Arsenal or other clubs in his coach career. They are both talented coaches recent years.
If Arsenal gets the chance and wins the Premier League, I am confident they will also win the UCL. Let's see how the competition plays out next season and who gets the opportunity to win the game. Arteta does not have the talent to coach Arsenal in the Champions League because UCL is different from other leagues.
Premier League is a domestic league and its competitiveness is less than Champions League with so many strong clubs around Europe. Winning Premier League is more possible for Arsenal than winning Champions League and at least they already ended two latest seasons as a runner up. One more step, one more big improvement, they will become champions.