Delete the 1.21 command structure

    In 1.21.1, you should reuse the normal 1.20.4 command structure that everyone knows. I want to update from 1.20.4 to 1.21 on my server, but updating all of the commands that my custom items use would take weeks. I learned the 1.20.4 structure and have known it well for a long time, now I have no idea what I'm doing. The trial chambers were a great idea and would definetly make my server more fun.
    Some other servers that I regularly play are also still on 1.20.4 because it's too much work to update everything, and risk corrupting outdated plugins.