Sometimes papers take a perspective that is completely outside your knowledge base. Again, ask a colleague to provide you with insight or suggestions for evaluating the quality. Otherwise, use caution in your critique describing things that did not make sense to you, but explaining your unfamiliarity. Suggest that the paper may be difficult for people without this insider knowledge to understand and ways they might make the paper accessible to a broader audience. Remember, your lack of understanding may not be a fault of the paper, but your lack of familiarity.
Papers are completely unrelated.
I have been a discussant for sessions with papers ranging from athletics to administrative teams to accreditation to student outcomes. Dig deep into the theme analysis, look for links. Even the most tangential papers usually tie to some larger themes such as diversity, policy, external forces, etc. When all else fails, drop the synthesis and admit the papers are unrelated, but pose interesting questions. Presenters who provide data or interpretation in their presentations that is not in the papers.