Comparing the 15 squad to the 17 squad is kind of pointless. The 15 squad was more physical but less creative. Pirlo was heavily depended on and he didn't always have a great game. From an offensive point of view, the 17 squad was much more dangerous offensively - what it lacked in physical solidity it made up for with its offensive outlet. So they are VERY different teams. In fact, I rate the 17 squad higher overall. I rated our chances of beating Barcelona before the final as very low while I was somewhat more hopeful for this final.
Alves will be a big loss next year. But if we can keep the 1st team players from last year and add new dimensions with Costa, Matuidi, Bernardeschi, Schick and hopefully a fit Pjaca - injury permitting we will be a LOT stronger overall. Other powerhouses like Madrid, Bayern, Barca etc are probably going to be as strong or stronger still though.