MythicCraft does not work on Spigot/CraftBukkit

Hello. MythicCraft does not work properly on Spigot or CraftBukkit. When the plugin is being enabled, it says it will disable any Paper functionality, but it seems to still use it. I am running on 1.21.1.

Server start up: https://paste.md-5.net/weyemibuqo.md
When I execute a command: https://paste.md-5.net/ufekoquwuj.bash
When I spawn a mob: https://paste.md-5.net/obuzecafal.md

The drops and message does not work too.