The debate over 21C skills should not be one between one set of curricular goals versus the other. This isn't core knowledge versus soft skills.
Riccards then goes on say that the need for students to have these skills (the ability to communicate effectively, critical reasoning, and so forth) necessitates certain teaching practices:
[O]ur focus should be on how we teach those core subjects that are necessary....How do we teach the social sciences in a manner that focuses on project-based learning and team-based activities?
This presumes that the effective way to teach the social sciences is project-based learning and group work. Perhaps it would be wiser to go topic-by-topic in the social sciences (and other academic disciplines). For each topic, teachers should have field-tested, proven lesson plans in which the learning approach is appropriate to the topic. Lesson plans that work -- lesson plans that are proven effective in getting the students to master the subject matter -- are what's needed. Students can only apply knowledge if they first have it.