FINALLY! After trying out every single channel blocker above this one on the search list, I finally found one that works. now, let's see how LONG it works; before YouTube breaks it.

Just found out it's not compatible with the "restore old theme of youtube" addon. That will break it! "youtube classic" works though.

11/11/2019 The new YouTube update broke it and now the red x isn't showing up.

11/12/2019 Problem solved! Thank you so much to the devs at Time Machine Develpment for taking care of that so quickly.

12/24/2019 A script in the addon is causing firefox to lag. Irritating, but not game-breaking