[cmrdporcupine]

We might be able to circle back to this now by putting some portion of memory and video on the die along with the CPU, but that was not going to happen for Atari and Commodore back in the 90s. Motorola wasn't going to shove 128KB or whatever of RAM into a 68k just for them, and even if they did it would have been so expensive

Memory speeds plateau'd while CPU speeds skyrocketed. Almost all the complexities of modern architectures have to do with this. There used to be "no need" for something as funky as L1/L2/L3 caches really because often your memory was faster than your CPU (hence why something like the C64's VIC-II or the Atari ST's "Shifter" are even possible).

Hell there were systems back then that didn't even have onboard registers in the CPU, but used external memory for it (TI's TMS series). The 6502's "zero page" is another example.

You can't do that anymore. The CPU will run many laps around your memory.

Still it'd be interesting to see what Jay Miner would have come up with in the late 90s or 21st century, if he was still around and in the game.