Amberol is probably one of the biggest hidden gems in GNOME apps. It's a simple easy music player whose background color changes based on the song's artwork.
Parabolic is another GNOME app for downloading videos from youtube using yt-dlp. It's super easy to use and even allows for multiple concurrent downloads.
mpv is one of those rare moments where using a proprietary implementation is objectively worse. Must install on any personal computer/mobile device.
Both are comparable in terms of video playback (both use hardware acceleration and ffmpeg) but mpv's appeal is that it's ultimately a minimal (as in lack of apparent GUI) command line tool rather than a fully featured application like VLC. I like mpv because of it's non-features which is why it's the backend for a lot of Desktop environment video players.
Amberol does hold up really well with high threshold music folders in my experience. I had a 24+ hours worth of music that loaded successfully in less than a minute.
Amberol has a "restore playlist" feature which loads your last playlist quickly.
Mpv is a good engine, but I prefer something like smplayer+mpv for all the extra functionality. I also like that VLC has tons of features, like full file/codec info and stats. I know there are other ways to get that info, but it's very easy in vlc.