pls excuse my stupidity, but what do u mean by a grasp of the "basics" as a background for astronomy? do u mean an understanding of basic physics concepts, like velocity and forces?
And then there’s the stuff you just can’t do, and that’s fine too. Like… I really don’t understand electronics. I struggle with it for some reason, and every time I learn I just can’t keep it in my head. I wasn’t that hot on general relativity either, which I thought was a bit more embarrassing considering I was going into an astro PhD, but my supervisor said “meh, don’t worry about it, I can’t do it at all and you probably won’t need it”.
Does that make a bit more sense? You need to study hard at some point, but undergrad is literally the most "stuff" you'll ever know in your life. After that it's more about remembering that you knew something once, being able to look it up and thinking to apply it to your work. Research is "open-book" ;)