Sure it isn't his fault he's been shifted all across the starting XI, and sure he may put the effort in, but the reality is he isn't a good footballer. I have seen him specifically make more mistakes this season than any player at United. How can any player, or fan, look up to him? His level of ability isn't good enough for a club of Manchester United's stature. Let alone captain.
Keane, Giggs, Vidic, Gerrard, and Terry earned their respect and led by example through years of elite consistent performances. Talent and confidence led to their consistency. They conveyed such a belief in oneself, they unconsciously made the players around them confident as well. Their presence automatically liberated their teammates.