What if you're a solo founder that has a cofounder lined up but are waiting for the right catalyst to bring them aboard? What if you're solo but have been contracting out the areas where you need help?
Making it into YC isn't impossible if you are. Many startups in the current batch are solo founder companies...Product Hunt, Filecoin, Lawn Love, Craft Coffee, etc. We would not reject a startup based on just ONE dimension or question. So if this is the ONLY thing you're worried about, you're in good shape.