@nogajun https://www.minecraft.net/en-us/article/minecraft-snapshot-22w17a search for "Multiplayer Secure Chat Signing."

1) You are free to disable it on your server.

2) If you do, any connecting client is *warned* you have done so.

3) Some plugins such as GeyserMC throw an error unless this is disabled.

4) Unless you can come up with specific, verified situations that are a cause for concern, you are simply fear-mongering and click-baiting. Stop it.