Planet, I would agree. However, I have seen many upbeat site owners take this approach only in terms of building links and come up very short.
Unique c class volume and diversity are still very important.
Content marketing is very time consuming work and having only content marketing driven links in our experience websites can be surpassed in SERPs. Examples of other links we build are important are
Chamber of Commerce
Authority memberships, associations, organizations
Local (where applicable)