It's impossible for video players to be exactly accurate on normal monitors as most computer monitors don't handle movie frame rates. Either a frame gets skipped or elongated here and there, audio get resampled while video speed changes, etc. but there's definitely no silver bullet due to imperfect hardware not matching movie data formats
It's relatively easy to get 100us level precision in CPU wait and mpv has 42ms (42,000us) to emit each frame (at 24fps). Nevermind that the monitor refresh is likely 60fps or better so each frame lasts for two+ monitor frames anyway. As long as it is consistent with each frame timing it should be very rare that a video frame is skipped or doubled up.
Frames shouldn't be skipped but if the monitor is at 60Hz and the video is at 24 then many frames will have to come early or late. That's what causes the stutter that is most apparent on slow planning scenes. It's like the reel in the projector is being fed through in a jerky manner so each from lines up with one of the monitor frames rather than going through at constant speed like it's supposed to. There's no way around this. However with 120Hz monitors you just display one frame every 5 frames and no jerky motion is required (except the fact that US releases are at 23.976fps, not 24, so a frame will have to be doubled every now and then I guess, or maybe the soundtrack is just pitched up to 24? Don't know).
A lot of monitors these days support a kind of variable refresh rate like Freesync, so this should be possible. I've never actually got it to work with AMD, Linux and mpv, though.
