I like anrimians music player, it is very modern, supports auto-play when headphones connect, and stop when disconnecting.
Its very minimal, there is MPV too which may be smaller than VLC but also supports streaming. VLC on desktop includes a ton of multimedia stuff probably stripped from the Android app. MPV is known to "just play media".
Fossify Music Player is also very modern, complete but small.
The most minimal for just playing single media files is one of the minimal dialog players.