Google, Facebook, etc, are marketing platforms. They are giving you marketing in exchange for content. It's equivalent to what you would've had to do in the past, which is pay somebody to go door to door selling your newspaper, giving out free copies of the newspaper. The free newspapers aren't your product, they're an ad for your product.

If you can't convert attention on Google/Facebook into your own ad revenue then you should stop purchasing advertising with content and you should focus on conversion.