If they want to compete they must have to spend more this season to bring in big players.
Until this season yeah, they really haven't been a competitive team for the league title. But in this season they surprised us all. Because we have known them in the recent years by making a good run for a while but starting to mess it up after a point. This time they kept being concentrated for a long time period which even helped them stay in the title competition.
But the messing it up thing happened again for them on the last weeks of the season as they lost many points. Maybe this caused them to lose their title chance but finishing at the 2nd position is still incredible. Maybe this is the start of some really good things for Arsenal. They are back in the Champions League after a long while. There is no way they aren't strengthening the squad more now in my opinion.