Good advice, emt. Although passports have gotten pricey, they're the best, and sometimes the only, proof of U.S. citizenship accepted. And they're good for 10 years for adults, so the initial cost isn't that high when pro-rated over 10 years.
I'm sorry you had to go through what you went through. They should have recommended a passport from the get-go, even if you were never married or once married. Although an original birth certificate and photo ID are still accepted under some cruise conditions, it can be risky even if it's good enough to allow you to board. If you're at a port in another country and have to fly home for some reason, you're going to have major problems if you don't have a passport with you.
Thanks for giving us the benefit of your frustrating experience.