You want to grow your startup? It's much easier when you Make Something People Want.
And I think Ralph Waldo Emerson obviously never built any mousetraps and has no idea what he's talking about.
Nonetheless, the saying does seem to apply well if you replace "Mousetrap" with "Donut" and "World" with "Portland".
If you can spot and build the next Google then you may not need marketing, but those opportunities are rare.