From what I gather about Save the Cat (having seen some videos but never read the book) is that one method for getting the audience on the side of your character is to show him sacrifice something to help someone else. (Point being, it’s not about saving the cat at all, but giving something up that you worked hard to get… but that’s a crappy book title.)
Classic example: Aladdin steals a loaf of bread and evades scimitar-wielding guards in order to enjoy it, only to then give half of it away to a pair of children who are begging on the street and are much worse off than he is. Now we like him, because even though he’s a thief, he’s not selfish and does good.
Enter the MC Problem of Self-Aware.
I’ve got a character entirely driven by his own selfish needs, and for the first time ever am hearing “I don’t know if he’s likable.” But I can’t have him do something to help someone else at the beginning because he had no ability to do that until the end of the movie.
In the pre-STC days, “make him likable” was solved by giving the character a dog. I can’t do this either. Why? Because his wife has a dog, which he later kills—on purpose, immediately turning off half of my audience.
So… what to do? Obviously, there are some people I will never win over vis-a-vis the dog thing, but I should be able to generate more sympathy/empathy/likability for the character before that happens.