This seems like an excellent example of the application of the Law of the Minimum - admittedly, outside of the specific ecological context it was formulated in, but the general principle is sound.

The resource in least supply will dictate the growth of the population, and the entity that requires the least expended or committed resources while meeting the minimum standards will dominate the population.

Fields that have low standards will be dominated by garbage. Fields with high standards will be dominated by whatever can pass those standards.

What are the standards that determine whether work in a field is valuable? Not from the viewpoint of those within the field, but from a general perspective? Once that's determined, we need only see which fields' requirements best match those standards.