You could also theoretically understand everything (with enough time and patience). Down at least to what all the chips in the C64 did, if not even the transistors inside them. That's what I miss, the feeling I was in control of my computer. Now the complexity is so high I feel like I can barely scratch the surface.
I feel really badly for anybody starting off today. The technology landscape is terrifying and it's really hard to know what to learn or even where to start. With a C64, you could master that machine inside and out very easily and while you were at it, really understand how a CPU works. It's amazing what they were able to do with a CPU with 3000 transistors (compared to the 50 odd billion in modern processors)
