Ads are a subset of marketing, so I don't really understand how that quote works but a good product carrying itself to a decent valuation probably has some correlation with how good the network effects of that product's user base are and how likely those users are to spread the word. At the end of the day you need eyeballs on your product, and organic growth is usually going to be the slower path(albeit not the worst path for some).

*If you have investor pressure to show growth(usually in terms of user base), you're going to opt for the faster progression.