We are born with the desire to succeed, to accomplish, to achieve. It is not in our human nature to aspire to failure.
Having taught, coached, worked with, and employed thousands of folks over a lifetime, I cannot remember an instance in which I thought a player, a member of the organization, or an employee intentionally set out each day to fail. Fail, some did. Some even failed with alarming regularity. But even those, I believe, desired to be successful in their endeavors.
Our job as leaders - parents, teachers, bosses, captains - is first to define what success looks like, in clear and simple terms (and no, it's not always in terms of games won, tests passed, or widgets sold). Secondly, we should be very aware of the progress of those team members, providing constant support, coaching, and instruction as they seek self-actualization through meaningful accomplishment. Finally, we should shower them with feedback and affirmation as they achieve their goals (and ours), whether incremental or monumental.
Only for those who demonstrate a persistent unwillingness and/or inability to get better should we be prepared to sever our ties with them. Even that drastic and painful step, however, does not necessitate our withholding of love and forgiveness toward those non-achievers. (Clearly, they were in the wrong role, and perhaps we own some of the responsibility for them being there.)