I'm rating this plugin a 2 (poor) due to lack of any functionality.

To start off with, I had to decompile the plugin to figure out what it did, due to the fact this resource page is not in English.
Sure, I could have translated it, but its a rule on SpigotMC to post in English, which this author decided to ignore.

Once I decompiled the plugin, I noticed there is absolutely no functionality to the plugin.
All thats there is a config (not in English) and a command to create/manage a clan.
But thats it. Theres no event listeners, or anything else.
Theres no chat handling.
Theres no damage handling (ie: between clan members)
Theres no land handling (I mean its not required, but I often see it in clan plugins).

The plugin really doesn't do anything, it just allows you to create a clan, and invite members to your clan. But thats it.

Im assuming the dev is wanting users to heavily rely on the placeholders to perform something like chat functionality?!?!?

I also want to note, the code that is here (for the command and clan manager) does appear to be clean, and well written... but at the same time it gives off AI vibes.
I feel like it's written by AI just for the fact that the plugin has no functionality, as if the dev asked the AI to create a clan plugin, but forgot to instruct the AI what the clan plugin should actually do.
I feel like if someone was going to spend the time/effort into building a plugin like this, they would have thought about adding actual functionality to it.

Summary:
Sadly this plugin fell short of that any sort of functional purpose outside of having a command to create/manage a clan.