No disrespect mate but I completely disagree with this line of reasoning. I think he is as responsible as anyone for being a bad captain and here's why:
We all know by now that under Pep, the players vote for who they want to be captain. If Walker gave them any indication whatsoever that he did not want to be captain, then either they would not have voted for him or Pep would have stepped in and made sure it went to someone else. Based on various quotes by themselves and other parties, we can safely assume that either Rodri or Dias would have been happy to step into the captaincy role if they were voted for (and probably others as well).
Walker was allowed to be elected captain for one of two reasons: either he wanted to be captain or he did not make any attempt to inform anyone that he didn't want to be captain, so in my opinion, whether he asked for it or not is kind of immaterial. I don't begrudge him that necessarily; liking the idea of yourself as the captain of the best football team in the world is the sort of trap that many world-class athletes would fall into.
Pep should take the majority of the blame for this as well IMO as I think we have enough evidence by now to suggest that players are not in a position to pick the best captain for the good of the club. And that's not their fault. If they vote for Dias or Rodri instead of the more experienced guy who has been here longer then they're opening themselves up to cause intra-squad issues.
I used to give them the benefit of the doubt and say hey, they deal with Walker every day and we don't, maybe they genuinely know that he is the best person to lead this squad - but I can't possibly still believe that's true. Clearly Rodri or Dias are better picks for captain. We see evidence of this after pretty much every match we lose anyway.
I am aware that to some extent this makes me sound like a real arrogant prick for disagreeing with the methods of (in my opinion) easily the best manager of all time. I want to be clear that, for me, this is the only policy Pep has which I believe is bad judgement. I would not be surprised if he changes his mind about who picks the captain at some point in the future. I fundamentally believe that it is not a coincidence that his players literally always 'just happen to vote for one of the longest-serving players at the club' despite longevity not really being correlated to leadership skills. I believe that they do it because they think it is wrong to snub a long-serving player at the expense of a younger one. I believe that the manager should have the power to make that choice because he is less likely to be argued with on the matter.