The revising of what is currently known would be daunting extensive work. That alone can create enormous skepticism.
"from the theoretical standpoint, the existence of this 4-neutron state is not much supported by the standard mainstream models of nuclear forces and its physical existence would also mean that the foundations of our understandings regarding nuclear forces and their interactions would have to be significantly revised."
"a team of researchers from the Technical University of Darmstadt in Germany has published a paper in Nature reporting the experimental detection of this strange exotic state. The team has thus confirmed its theoretical prediction which was made 6 years prior to this experiment."