It changed because we didn't have Fabregas anymore, we can't play tactics that were totally dedicated to making him the focal point of the team if he isn't here.
For that reason now I'm not sure who Wenger will build the team around, wilshere isn't fit yet and van persie has left/leaving.
There wasn't a big star in the midfield last year and to my mind it was supposed to be Song-Ramsey-Arteta sharing the defensive and attacking duties which wasn't like when we had Fabregas attacking and Flamini covering for him for one instance. Last season there were times when Ramsey stayed back while Song attacked or Arteta stayed back and Ramsey attacked, that sort of midfield tactics will serve us well in the long run. The only problem with it is when Arteta was out we didn't really have anyone who was willing to sit back as both Song and Ramsey or Song and Rosicky were trying to attack at the same time.
This may sound silly but I prefer the midfield we have now to the Song-Denilson-Fabregas one where Cesc ran the show, Song was a pure DM and denilson I'm not sure what he actually did but his role was as a cm. In that season we played DM-CM-AM and now it seems to me like we're playing with three CMs and three forwards. I say that because our wingers are always swapping position now and there are times when Gervinho has been through the center with Robin on the left, I don't know if we're doing this to confuse the opposition or if it's just due to our front three running all over the place but it was what it was.