I actually did Engineering but work in code every day. I noticed much the same as you: it's a million little topics. Control theory, thermo, digital filters, a bit of coding, and so on. But having come at it from another side, I figure the lesson is that you can learn any topic you like, the procedure is the same. Read something, try it yourself, search for solutions. If it's hard look at the prerequisites.

I suppose it's a bit more obvious when you study Engineering that you're not going to use all of it. But after a few years you realise that you use a lot of it. There's this meme going around about "The 20 most important equations". I think I used them all either at work or in uni.