I had a sidecar with my Amiga 1000, which allowed you to use an XT MFM hard drive + controller card for the Amiga side. Once kickstart + the software loaded, it was incredibly fast. It was weird having a full IBM PC + Amiga in one conjoined machine.

But I agree that predictable slowness is a thing. One only need to discuss traffic jams vs a 20 minute car trip without them.