Second chapter becomes the first chapter if you throw away the first chapter, should you also throw that away? I guess Zeno would approve. Vonnegut's advice and most if not all of the common advice given to aspiring writers has truth in it but it tends to be too pithy for its own good. The first chapter needs to lay the groundwork for everything that follows and this applies for everything from genre and essays to the complicated and experimental works of literary fiction. Why should the reader care?

Vonnegut is ultimately pushing back against the old saw of the captivating first sentence, many aspiring writers fall into the trap of trying start their book by trying to captivate the reader at cost of laying that foundation; if I can just word this opening paragraph perfectly, the readers will be hooked. It is a fairly dishonest way to go about things. Everything the reader needs to know about what you are writing needs to be covered in that first chapter or paragraph or chapters or section or whatever metric applies to what you are writing, the trick is that you need to present it in a way that does not spoil everything to come.

If you get fixated on captivating the reader with the opening, tossing the first chapter and reworking the second is decent advice, but it might be better to just rework the first. All of these pithy bits of writing advice have truth in them and have a great deal to teach you but far too many aspiring writers tend to accept them as dogma.