If a publisher rejects your novel, should you change some of your novel?

If it's something innovative, like fixing the grammar or flow of the story, I'd say you should try your hand at changing it since those are things that generally make it better for everyone who reads it. If they just want you to change things based on their personal qualms about it though, I'd say no. Get opinions from more than one publisher so that you see where you stand, and then decided what you want to keep or change.