So the cosmic rays they are describing being deflected are charged particles, usually protons and nuclei. As these charged particles travel through the magnetic fields, they are deflected, and some fraction of those arrive at Earth. Take into account the vastness of the interstellar space in the Milky Way and how the magnetic fields can change over this expanse. Now you have charged particles entering a massive, non-constant field region, which makes things difficult, but not impossible if you were able to perfectly model the field (which is still outside our capabilities, as we can’t even perfectly model the fields between Earth and the Sun). Add onto this the fact that cosmic rays have varied energy, velocity, mass, charge, and are being produced at random angles from their sources, you have a fundamentally randomized system with cosmic rays arriving, seemingly, from empty regions of space.

Neutrinos solve this problem, because they are neutral particles and only interact via the weak force, so they ignore electromagnetic fields and can pass through huge amounts of matter without interacting. This allows them to travel through space freely, not being scattered by dust and ignoring the magnetic fields. Previously photons were really the only way to get a picture of the stars, but now IceCube has shown that neutrinos produced when the cosmic ray interacts near its origin can do it too. I hope this answers your question!