Are people incapable of change in an inspector calls?

Yes because the Inspector is a very ambiguous character. He could be the voice of Priestley, due to the manner that he interrogates the Birling family while he also could be the voice of God. He could also be fascinated with death, as "Goole". reminds us of "Ghoul" which is a death associated character. He creates at once an impression of solidity and purposefulness