As your team grows bigger, there will always be incompetent people in it, and chances are that everyone will know who they are. When this happens, if you don’t have the will to improve them or to fire them, then don’t go about broadcasting their ineptitude, because you’ll have nothing to gain from it.
In fact, it comes across as an insecure attempt to make you look better, whenever you talk about the incompetence of a teammate behind their back. The truth is that when you talk behind people’s backs, it will inevitably come back to bite you in your (you know what). Your callousness will make others have negative opinions of you, and speak about it behind your back, as well.