What it doesn't do is make you a better writer or guarantee that your novel is good enough. Knowing people doesn't get your book published if it's not a book that someone thinks can be marketed and sold. But don't let anyone tell you that it doesn't make a difference. Knowing people can make your path easier. It can get you taken more seriously. It can help you understand where you want to go, what to expect when you get there, and how things work or don't work and what you can do about it.
And it's not that hard.