Rated 2 out of 5 stars

Pros: I still don't know if there's any...

Cons: Doesn't stop or prevent YouTube videos from autoplaying on YouTube site. Useless against YouTube videos embedded on blogs.

This review is for a previous version of the add-on ( 

It's not meant to stop embedded videos, as those are not supposed to autoplay anyway.

As for not stopping videos on YouTube, make sure you don't have other add-ons that might conflict with it, and try disabling and then enabling the add-on.