Neutrinos are so hard to detect we don’t know much about them. So this can give us more information about how they act and interact. That leads to a better understand of physics in general.

For example the first solar neutrino detector only detected about 1/3 of what it should have based on how many the sun should be producing.

That in part lead to the discovery of neutrino oscillation. They change flavor between the three types. The sun produces one flavor but they have changed into all 3 by the time they get to Earth.

This may show us for example if there is any flavor asymmetry. Plus a general improvement in cosmology.