Its a major accessibility issue for me, I've got a visual input processing delay (the input processing delay is in my brain) that makes it impossible for me to rely on visual inputs for timing, so I'm consistently being thrown out of sync by 808 flashing because each flash occurs before I can finish processing the previous. I can usually get around this in other games by letting my vision go out of focus briefly, or just ignoring the visual cue and listening for an audio cue instead; problem here is that 808 is always flashing, so I have to avoid focusing my vision at all if I want to actually land the timing of my attacks.
Put another way, 808 flashing is a piece of visual noise so loud that I can't hear anything else. I have the same problem with actual metronomes, looking at them makes it impossible for me to keep time (solved easily by keeping them out of my line of sight). Please add an option to disable 808's flashing.