Crypto mining with fpga was in the weeds down this path, or 100 Gbps signal processing. Two examples where low level stuff is still relevant, just not commodity and widely available like the 8 bit micros were.
I also read a high frequency trading blog that was posted here a few years ago. Same thing: hacking hardware and software so the first bytes of info could be grabbed from a stream and acted upon, instead of needing to wait for the whole package to have come in.
Also when I was in the demo scene on the Atari ST one had to do specific timings in the assembly code to be able to draw outside the screen's borders (so the borders were on screen but couldn't be drawn on by code).
