I just always think Arteta is not a right manager to win trophies for Arsenal. This season as started and they start with good form if the season comes to the middle you will see there performance will definitely reduce but let see how the season own will be since they have key players in the club currently and can help them perform better in the league competition. Let see if Arsenal can get the chance this time and win the league title.
Last week, I heard a Chelsea fan rooting for Arteta to win this year's league title, but was met with similar response as you stated. The team is strong and effective, and could win tough matches, yet can't withstand the pressure of multiple leagues. If Arsenal is met with the champions league, and premier league combined the players begin to gas out and face injuries. That is where Arteta must look into for his boys to be strong enough to play multiple leagues without much casualties. If that is fixed, Arsenal will most definitely be a strong match against competent teams like Liverpool.