Preface
Today, as usual, I launched my 1.16.5 vanilla MC instance and went into the game and casually /located a village.
However, a snippet of error appeared in my prism console after the command: https://pastebin.ubuntu.com/p/Y4q75JMv8g/
SMCFix
The mod simply patches the map in StructureManager to be ConcurrentHashMap and fixes this.
This CME won't crash the game, and in any case, it's rare. So, if you are not constantly struggling due to this exception, you don't really use this mod.
Or maybe you just want to perfect your game a little bit? Then use this mod, no one will stop you.