I thought the following BMJ Perspectives article that removes meta-analysis from the so-called “evidence hierarchy” would be interesting to readers of this topic:
The New Evidence Pyramid.
Blockquote
Therefore, the second modification to the pyramid is to remove systematic reviews from the top of the pyramid and use them as a lens through which other types of studies should be seen (ie, appraised and applied). The systematic review (the process of selecting the studies) and meta-analysis (the statistical aggregation that produces a single effect size) are tools to consume and apply the evidence by stakeholders.
That is a much more philosophically defensible position, than treating meta-analysis as comparable (or even superior) to primary data reports.
I hope we can quickly move from focus on a single effect size, towards a more useful idea of a range of distributions for the effect, so the formal Bayesian apparatus can be used to design experiments that will settle disputes to the satisfaction of the relevant parties.