The theories that we were dealing with around the dawn of QM/GR were relatively tractable; we could make long-enough-term predictions about the behavior of many

The theories that we were dealing with around the dawn of QM/GR were relatively tractable; we could make long-enough-term predictions about the behavior of many systems and we had a library of observations that clearly and reproducibly deviated from those predictions. We had even begun to draw vague correlations among the diverging data. Today, we have experimental data that diverges from predictions... regarding... the number of neutrino collisions we can observe in certain giant tanks of highly pure liquids, and... the scale of variation in the cosmic microwave background and long-range mass density is too small, oh, and... galaxies rotate kinda weird... free neutron lifetime measurements disagree by about 1.1%.... there's not quite enough lithium in the Universe (no, really)... good luck tying all this together into a theory of everything!