Arsenal eliminated from the FA Cup reduced the number of competitions they participated in, the Arsenal could focus more on the EPL and UEL as targets to be achieved at the end of the season. Arsenal also avoided a busy schedule that often injured players due to fatigue. Arteta could minimize the risk of injury to his players by focusing on just two competitions.
Even though Arsenal have two other competitions such as the Premier League and Europa League, their failure in the FA Cup should be considered setback.
You may need to know that Arsenal are the first team to win 14 FA Cup titles to date, they have reached 21 finals in those 14 titles. So it's only natural that Arsenal's failure this season in the FA Cup is questionable following their good performance in the Premier League.
Arsenal are now focusing on the Premier League after winning 5 points from Manchester City, Arsenal chances are very open to maintain their position until the end of the season. Arteta can rotate when his team has the upper hand against weak teams, he can withdraw the main players to give him more hours of rest and keep his condition fit so that he is better prepared when playing in big matches.
Now there is no other choice, Arsenal must focus on the Premier League and Europa League. Those are two competitions they are still likely to win this season, but I don't expect Arsenal's march to the title to be easy.