We were definitely weaker from the point those players started out from. The likes of Barzagli and Bonucci were nothing close to their current standing. Neither was Marchisio. Matri was nothing more than a decent striker, and Vucinic a good-very good one on his day. That Chelsea front three is miles ahead. Our starting midfield is ahead.
Also, you are only comparing starting XIs, Chelsea's squad overall is stronger. We had very little quality off the bench - a waning Del Piero was one, then the likes of Quagliarella, Borriello, Giaccherini and the outcast wingers Elia and Krasic. Chelsea have Willian, Fabregas, Batshuayi, Terry etc. But it's not surprise given the financial difference between the two sides at those points.