Yaya moves plenty and always has done but it has often lacked the level of intensity Pep wants (or supporters have wanted to see). However, no one on this forum actually knows if Yaya can imrpove his fitness sufficiently to play a part or how much a difference a change in attitude might make. You certainly don't know if Yaya could still play a valuable role off the bench.
I cant see how Yaya would not be a valuable option to have coming off the bench in certain matches. But it would depend on whether he would be prepared to accept that role.