I am not sure that Gyokeres will be able to perform as many people expect because the Premier League is a different beast from the Portuguese league, and in Portugal everybody was playing for him. At the same time we can't judge a player who just arrived at a new team, especially during the summer friendly matches where the result doesn't matter at all.
Some people are judging the club friendly match thinking that is how the main competition will go which is not suppose to be view like that, I feel like some teams don’t even take this friendly club match to some extent because how I see their performance. it’s just a pre-season matches that they are playing, and for Gyokeres the player is new to the team and he need time to get adapted to the club and how the style of their play works, so we can’t expect him to give us what we want in a very short period of time.
That's the risk of being a big club. Even in friendly matches, they're required to win; if they lose, there's going to be a lot of criticism and even doubts about Arsenal's performance for the start of the league. This is just a friendly, not the Premier League, as you said. Furthermore, we know that friendlies are always a platform for coaches to test strategies and develop chemistry with players.
Arteta has certainly assessed the areas that need attention and addressed them. In my opinion, it's better to lose now so we can see the weaknesses in each department. Moreover, Arsenal have been playing without a true striker for a long time, and now they need to adapt to playing with Gyokeres. So I think Arteta knows he has work to do before the season starts. If you look at the friendly, Arsenal created so many chances, but they weren't effective in capitalizing on them.