Part of the reason that we don't completely dislike Scrooge is because of his universality. There is a universal appeal to Scrooge. The reader recognizes that Scrooge is uniquely human. Scrooge sees the contingent and temporal as universal. From the exposition, we recognize that Scrooge fails to realize that which is transcendent. We know that there is something within him that has failed to be activated. It is for this reason that we cannot completely repudiate him. Scrooge has something within him that is locked away. The reader recognizes the need for this to be unlocked. In waiting for the key, in some form or another, the reader recognizes the frailty within Scrooge.
Part of this resides in the fact that Scrooge does not do anything in the name of money that is permanent. Scrooge rejects people, is curt with them, but he does not engage in any act like savoring emotional cruelty, or physical acts of brutality that makes him completely irredeemable. Scrooge acts in a way that is not entirely desirable, but he does not do anything that truly offends our sensibilities to a point where we cannot see change being evident. It is because of this despite Scrooge's mean and miserable ways that we never completely dislike him.