To be honest, I'm struggling right now. That one statement, that one promise that my work is going to be rejected out of hand by someone who hasn't read the whole of my work, has made me doubt myself. I've tried not to let it get to me, but it is. Those statements which contain a grain of truth, or a seed of our fears, always hurt most.
So, if all you can say about my work is that it's unoriginal, flat, and going to be rejected out of hand because of the content, keep your mouth shut and your opinions to yourself. As I see it, the only way to fail to get published is to not keep going. Not query agents that represent your genre. Not work to write the best possible book you can write, and then be willing to go back and make it better.
If you've ever had someone tell you you're going to fail, you know what it's like. Join me in flipping them the bird and then marching on. Because I'm a writer, and the low opinion of one person out of a dozen will not stop me from doing what I love to do.