Unserviceable.

Of persons: Unable to be of service; not rendering service or help; useless.

Of persons: performing no worthwhile role or service; of inadequate or insufficient ability; incompetent, inefficient.

Scottish. Of persons. Of little use or worth.

(un-, prefix1 affix 1.)

Of a thing: valueless, futile, feeble. In later use chiefly of a person (or a person's actions or attributes): lacking vigour, energy, or capacity…