Update Skript to the latest stable version [for 1.12 servers] - Skript 2.4 or Skript 2.4.1
- https://github.com/SkriptLang/Skript/releases/download/2.4/Skript.jar
This is the recommended version for 1.9 and above so there's no reason to use an old one. It works perfectly fine and will add a lot.
I'm not aware of any reasons not to update it