It isn't about lack of effort. The problems with Alves' wing is twofold.
One, Alves is not the same player he used to be. He is slower and less quick now. Recovering his defensive position takes him much more effort than it used to
Two, and this is the biggest problem IMO, the defensive structure of the team has changed, and what was designed before to cover Alves' back when he went on attack, now no longer offers cover.
Alves was always in the attacking third for Barcelona, in this way his game has not changed. He is playing now the same way he always did, with of course the caveat that he has lost ability due to age. However he no longer has a defensive structure of a back 3 to cover the space behind him and allow him to recuperate.