This is a specific version of a more general problem, namely that scientists only study what interests them, therefore there are gaps in what gets studied. The

This is a specific version of a more general problem, namely that scientists only study what interests them, therefore there are gaps in what gets studied. There are fads in scientific research, just like everything else people do. Not sure what the solution is (more diversely targeted grant funds for basic research?) but we almost did not have an mRNA vaccine because mRNA research was not popular at one time. I'm not sure there are even surveys to identify these gaps. You occasionally see papers or articles about "open questions in discipline X" but those are still only aimed at popular research interests. Truly identifying gaps in research direction is partly impossible for areas no one knows anything about, but it seems like a group of people with deep knowledge could at least create a partial map of the territory. The microbiome probably remained unstudied for so long because it was a "yucky" area of research that no one wanted to study. Research into cures for liver diseases were not popular because "they would just encourage people to drink". I'm sure there are many other examples.