There are a lot of great insights in this article from the Search Engine Journal. It's called It’s Time to Put the 'Marketing' Back in 'Content Marketing'.
There are really thought-provoking points here. This one's particularly interesting:
Content marketing without promotion is just content.
For content to drive meaningful results in a reasonable period of time, it must be promoted via other means than just search engines.
Content created just for the purposes of attracting links is better than content without even that goal in mind, but attracting links is just one of the many benefits of ...