It doesn't let the audio clip/exceed safe volumes and always applies some sort of a limiter, even if it's disabled everywhere in the settings. Try using an EQ on a bass-heavy track and see that it's limited.
Try jumping back multiple times in a song at its beginning, and it will play in lower pitch.
I thought VLC was awesome while growing up, and at the time it probably was compared to Windows Media Player and such. I remember a common bit of praise was that it supported more types of video files. I haven't really run into anything mpv won't play (I even use it when an image I saved ends up as .html for some reason and then use the info screen to determine the real extension it should be so I can rename it), but also I'm guessing we've standardized more on codecs and containers these days which doesn't hurt.
BUT mpv still isn't perfect. The script in https://github.com/mpv-player/mpv/issues/8463 is really needed to handle some stuff (mainly clandestine anime) and the libplacebo/gpu-next transition wasn't exactly the smoothest (my config still has hotfixes for https://github.com/mpv-player/mpv/issues/10716 and https://github.com/mpv-player/mpv/issues/14474).
Nitpicking aside, it really is the new gold standard these days, and for good reasons.