Vilhjalmur Stefansson

The philosophers of the Middle Ages demonstrated both that the Earth did not exist and also that it was flat. Today they are still arguing about whether the world exists, but they no longer dispute about whether it is flat.

Hammer down product fundamentals first. Make sure you've got something that works before doubling down on promotion and marketing. Create a groundswell of organic support, and only then leverage PR and advertising to spread the word.