Hoi,
The notion that Commonists are second class contributors is plain wrong. It has not been said, certainly not by me. Commons as a project provides a service to all projects in a similar way that Wikidata does. When you compare those two to the "other" projects, the others are insular what they do from a community point of view is largely irrelevant in the wider community.
It is exactly the fact that Commons and Wikidata are sharing their resources that gives them the potential to be a more social project, more inclusive. It already has the shared relevance, when its community "gets it" that its actions have a wider, more global effect, it may become more sociable and thereby more effective.
Thanks.
GerardM