It works but not 100% accurate but gives you a rough estimate.

The number shown is an estimate, not the actual number of dislikes. The methodology to get that estimate is a bit questionable due to sample-bias.
Furthermore, the extension stops working every month or two.

Does NOT show the dislikes of Youtube videos.

Completely makes up it's dislike count.

thank you. a disservice to the general public from youtube for removing dislikes