It should be obvious, but we miss it.
Making the greatest product, offering a revolutionary service, or serving the most desperate need are all a waste of time if no one wants it, uses it, or supports it.
I'll say it again - your mission is a waste of time unless it's funded.
If you start here, marketing becomes your mission. (And your classic 'mission' becomes operations, execution or practices - nothing much more.)
Marketing is your mission, or your mission will always struggle to survive.
It should be obvious...