Arsenal have not had that quality all this time, which is why they have been failing to win trophies this season. You can see they were lacking something, and it really affected their stability in performance for a long time.
However, it is great that this season they have done what is necessary to strengthen the team, and now Arsenal can easily achieve some targets. If Arsenal had understood the importance of signing these players long ago, during all those seasons when they were close to the top, they would have won one or two trophies by now.
Arsenal is finishing as runner up in last three consecutive seasons of EPL and in last UEFA champions league they were eliminated in semi finals after beating Real Madrid in quarter final. Arsenal is not a weak team as they have everything that a good team should have, the only problem with them is they fail to perform at final stages of every tournament. This is something the team management should have to look and improve. Just adding more expensive players to squad won't solve the problem.