What you said is true with Liverpool they came into the match with much determination on winning the match than Arsenal were looking like. Liverpool didn't have many chances but when there was a very open opportunity to get a goal they maximise it. I have skepticism on Arsenal having this season flow in an incredible way for them, it is going to be harder for them than previous season despite their buildup particularly with how many others clubs have made their squad tighter than how they were.
At every season, the chances of every team building up their squad against the next season is always high, so I see that as not a big excuse for Arsenal not to perform well this season. They have come so close to winning the Premier League not once or twice and they always fail to win it. Every season they build up a better squad than the previous season, but they still fail to win anything in the end. They need to apply a lot of professionalism and dedication this season if they really want to even come close to winning the premier league title. They failed to win the match against Liverpool, their top rival of last season but that should not make them feel reluctant of not triumphing this season. They need to put their heads up and fight for that title.
In my perspective losing their last match against Liverpool is not the big deal. The team needs consistency. They have been playing well for a long time and then they broke down in the end or middle stages. If the team's players cannot play with pressure when they are facing top opponents, then they will fall behind in the title race. Arsenal are undoubtedly a good team but they cannot do well at the right time. To develop the team strength If someone in the team is injured, then they need to have better players as back-ups. Apart from that, they need to have good clinical strikers, otherwise no matter how good the squad is, the results will not be good. The team needs to perform consistently throughout the season. If they can take a strong position mentally in big matches, then they will definitely be able to do well.