Astrophysics and cosmology are both relatively straightforward. There is one set of partial differential equations that are relevant, a few more when you also want to understand things like the magneto-hydrodynamics of stars or charged gas clouds. In the end it is nothing you can't manage to understand with a bit of study. What is truly hard is to prove rigorous mathematical statements about any of those equations and the resulting geometry. But the number of people who attempt this are dwarfed by the total number of people working in this field 1:1000 maybe.

I mean, what's behind the curtain of most things is "a bunch of differential equations".

With things like astrophysics you also have "and computer simulations".