Merely noting that this exact thread came up about five years ago.
Would suggest that whether McDavid is a good captain isn't the right question, but it is whether McDavid is a good leader, which isn't exactly the same.
As was related repeatedly in the earlier thread, the problem with this inquiry is that the only persons who could really answer this question are his current or former teammates, and they are not participants in these HF discussions. Nobody but them knows what goes on during practices, in the locker room, the in-game chatter, or what is said or not said at the steakhouse after the game.
About the only thing that can reasonably be discussed is whether McDavid's efforts towards leadership manifests itself on the ice. Otherwise stated, does it seem or not seem that McDavid motivates his teammates to elevate their on-ice play, other than the raw application of his own natural talents? But even that seems pretty speculative one way or the other.
Perhaps a more worthwhile discussion is how McDavid compares in this regard to Matthew Tkachuk who is obviously a leader (if Matthew Tkachuk isn't a leader then that term has no meaning with the NHL).