Not only a striker but I think Arsenal needs a star player or an experienced player who can lift the team's mentality to be able to perform optimally, Arsenal's problem in the last 2 seasons is not only with the players but also things outside of that that cannot be controlled so that Arsenal always struggles at the end of the competition as if they cannot play as usual when under pressure.
They truly need a world-class striker in latest seasons but they have never bought such as consistently goal productive striker for their squad enhancement. In this summer transfer season, and as preparation for a next season, Arsenal truly need to improve this position as their main priority. If they fail to improve their striker position, they will again struggle in Premier League title competition with other clubs in Premier League.
A last season did not show any improvement of Arsenal but they actually declined a lot while they fortunately still managed to finish with a runner-up position. Whether they can get a good striker in this summer will decide their ability to compete for top four and also Premier League title in a new season.