Older studies often reflect the evolving nature of psychology as a field. While they may not meet today's rigorous standards, they can still provide some valuable insights if approached critically. They can be cited as part of the historical progression of ideas. But it's important to acknowledge their limitations while noting their role in shaping current research. Just clearly specify that the study reflects the norms, tools, and methodologies of its era. ALSO check if the findings have been replicated or expanded upon in later research. This can validate the study’s relevance or highlight its shortcomings.

Imagine reviewing a 1970s study with 7 participants exploring cognitive load. While the small sample size is a red flag by today's standards, it might still have contributed foundational ideas. In a literature review, you could write: "Early research (e.g., Name, 1974) suggested a relationship between cognitive load and task performance, though conclusions were drawn from limited sample sizes and simplistic designs. Subsequent studies (e.g., Name et al., 2000; Name, 2015) have built upon these preliminary insights, employing larger samples and advanced analyses to confirm and extend these findings". It's just an example. How you frame these studies depends on their relevance to your specific argument and their place within the broader research landscape. Hope it helped.

Older studies allow researchers to know how the topic progressed with time.

True, but that was not the question. The question is whether they should be considered evidence of something, even if they do not meet our contemporary quality standards.