Not saying rules encoded in "if-elses" are good, but they can put all the rules in one location. Polymorphism can spread those rules out in somewhat obscure ways. I use both, depending on what I want to do.
Right, I wasn't saying polymorphism was the only solution. I was saying deeply nested if elses are hard to maintain. There's many solutions to avoid them. So I think we agree, use what makes sense given the context.
