You need to get a permissions plugin and setup permissions on your server. The reason you can use the command when your opped is because, by default, most plugins give opped players permission to use all commands.
Luckperms is a good permissions plugin to use, here's a good place to learn how to use it: https://github.com/lucko/LuckPerms/wiki
Here is the list of permission nodes for EssentialsX: https://essinfo.xeya.me/permissions.html