Learning assembly and creating my own simulated processor using multiple layers of logic gates was one of the main cornerstones of my college education. I remember when things finally "clicked" and I finally understood how computers worked on a fundamental level, I was positively giddy for days.
Unfortunately, our technology has become increasingly complex. For a while I tried my hand at learning more about modern processors, but found it far too overwhelming. Maybe I just didn't know where to look for more approachable resources. Just taking a look at the reference manuals provided by Intel is enough to make anyone lose hope. I seriously doubt any single human is capable of reading and understanding that in any reasonable amount of time.
If you wanna go down into the metal, consider picking up a microcontroller and writing your own firmware. You can ditch the OS and start squeezing every ounce of power from the hardware. It's pretty crazy how little power a well configured microcontroller can get by with.
I'd also suggest learning WebAssembly! The text format is quite pleasant, and it does away with many of the issues you'd have to deal with when using real hardware. Even better, the spec [0] is actually quite readable for regular developers. That might let people get their feet a bit wet without having having to go into the deep end of the pool right away.