the high level of inconsistency is the major difference between arsenal and Manchester city side that has won the English premier league title in the past four seasons if am not mistaken, because the quality is also there in these arsenal team, but they are just too inconsistent to compete.
Just as you rightfully pointed out, they became inconsistent when it really matters, towards the end of the season when everyone is giving their best hoping to finish strong and win something, but in the case of arsenal, they will be inconsistent during that period, so as it stands now, if they really want to win the premier league now or in the future, they just have to start ranking up the winnings and be as consistent as much as possible, and be hoping that Liverpool will drop point along the line, because right now, they are actually in a tight Conner due to their inconsistency.
That is their problem, for 2 years in a row they were very close but lost, same happened with Liverpool in the past as well, they were decent but ended up with a bad move and not really a good return at all. We should require how to get better at this than what we are seeing at the moment. I believe that we are going to see a much better return with time, but that doesn't mean that we are not going to see this get a better return in the end.
Hopefully, we should be considering Liverpool to make a comeback this season, so far they are looking good and City has a lot of players that are injured so we could maybe see something changing, we could maybe see Liverpool finally getting that title again after so many years of City domination. In the end, Arsenal has to wait some more, they had some injuries this season and that means we are going to see them not have that much of a great return and could be considering the situation changing a bit more.