We can disagree on this point. I'd say you can have the best solution, best possible product, best idea, and best people building it, and if you have no capital, you're toast.
If you were the only person on the planet, then yes.
But X and Y still have option value. You can sell them our service them to others.
You can keep them, and continue looking for Z.
But X and Y are not valueless. You are just trying to take them in a direction (needing Z) that isn't deploying that value (until you get Z).