People are weak and prone to sin, but that is a different concept than being inherently sinful. If that were true, how could Christ be fully man?
Literally, because it is a miracle.
Was Adam sinful before the fall?
Hebrews 4:15 For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin.
Was Adam fully man before the Fall? Of course. Sin does not make us fully Man.
Jesus is fully man because sin, while that inclination is present in human beings after the Fall, is not essentially part of human nature. Ask Adam.