I don't think the concern is that Davis "did it for the money", and that's not a fair representation of why some of us mock Jim Davis.
I don't think anybody is arguing comic authors shouldn't make money out of their work.
The concern is that Garfield is the product of conscious market research and not whatever we imagine a comic artist goes through when creating their comics. You can dismiss this as some ridiculous search for "purity", but wouldn't you say most people imagine Watterson, Schultz, etc. went through a process more or less "I liked these other cartoons, and wouldn't it be cool to make something about <idea>/<childhood memories>/<something that inspired me>/<something that worries me>" vs "hey, let's make money, what kind of character would make me the most money?".
Davis is not the only one, of course.