The whole concept of a captain is massively overrrated. All of our players should be leaders. That's the case in the best sides. It's a symbolic role. That said, far better to have a world-class player that everyone admires going up for the coin toss and handshake with officials to set the tone at the start of the match than somebody who, while honest, struggles to pass a football.
People go on about Kevin Ratcliffe as an ideal captain. Thing is, Ratcliffe may have had a role in the dressing room, but that side was full of leaders (Reid, Gray, Southall, Bracewell, etc.). It's massively overrated - but it's symbolism has a value. Our image should be impressive. Not Seamus Coleman.