Can a person be accepted as a Divine appointee just because he claims that he has received a revelation from Allah?
Such a person has to meet a number of conditions. The first condition is that he appears with the correct message at the time that he is needed.
If the need is to prove that the Emperor is a human being and not god there is no point in the mujaddid trying to prove that Jesus is dead.
God does not send down a new person until the mission of the old one is no longer relevant. The mission of the Promised Messiah still continues because, to give only one example, both Muslim and non-Muslim still do not understand the real significance of what jihad is.