Well, Giroud looked really poor last season too. I think he just needs some time. He did really well in Spain last season. I want to see him given a shot.
I don't think Giroud was as bad as Aspas. The main problem with Aspas IMO is that he cannot take the physicality of the EPL, he has good skills but too lightweight and too slow. In Spain it works because all players take their time to build their game passing around patiently, relying on their skills. Also, you have players who get one good season but cannot build on that, especially when changing environment. Giroud is physical, this is what helped him. Coutinho on the other side is as lightweight as Aspas, but, much quicker both in thinking and execution. Don't think Aspas will make it unless may be he gets a very physical partner to play along.