The coach should not be completely blamed when the team's performance does not improve, because the ones who should be blamed in that case are all parties involved in the team which of course includes the coach as well. Because the coach's role in the team is when giving tactics to all the players who are already in the squad, so don't say about the coach's role or not in a team because that is really inappropriate to say.
Of course, all the parties should be blamed but the coach is indeed the one most responsible for the improvement or the decline of a team's performance. The coach is the one who chooses the players, decides the formation, and sets the tactics/strategies. These are major factors and these bring direct influence to the team performance.
Yes, Arteta was appointed as Arsenal's coach since 22 Dec 2019 and his contract ends until 30 June 2027, not to mention if there is a contract extension. So yes, Arteta already understands Arsenal's characteristics and needs very well. It's just that, unfortunately, Arsenal has only won a few trophies with Arteta, but Arsenal still keeps this coach.
I guess Arsenal will get a contract extension. Even if Arteta still can't win EPL trophy
wtih Arsenal, he is quite successful
in managing Arsenal. At least, Arteta almost won the EPL trophy several times.
In the last 3 seasons, Arsenal always stays in the 2nd place in EPL standings. It indicates a big progress for Arsenal performance, Arteta deserves to get appreciation. In addition, Arteta even won a trophy of FA Cup and English Super Cup with Arsenal. I think Arsenal board feel quite satisfied with Arteta.