I don’t hate a prologue. In fact, I can absolutely love a prologue. The problem I see for debut authors and those submitting to agents, or at least to me, is that the prologue is often used as a crutch. It’s an easy way to fill the reader in on backstory so that you, the author, can write the real book.
My suggestion to dump the prologue doesn’t mean you need to throw it away for good. Instead, put it in a safe place and decide later if you need to use it, but decide way later, after you get an agent and after you’ve finished the book. Decide at that time if the prologue is a crutch or real added value.
No matter how great your book is as a whole you will be judged by agents, editors, and readers on those first pages. Is your prologue the strongest and most exciting writing you have? Will it grab the reader and suck them in for 400 more pages?
When submitting a query to me, and to most BookEnds agents, you will be asked to include sample pages or a sample chapter. In this instance, you should always include the first chapter (not the prettiest from the middle of your book), but I would suggest it never be the prologue. I rarely feel like the prologue gives me the meat I’m looking for when getting a feel for a writer’s work. It’s not typically the author’s best foot forward and it’s not usually what grabs me.