This is a question for the different dev teams is it not? Your question is about the add-ons and not the browser. Just looking at Clean YouTube, it hasn't seen an update since 2018.

Of course Firefox/Mozilla isn't directly responsible for the proper functioning or not of the Addon/Extension offered. That said it's quite possible for them to delete those whose updates are too old. I add that this doesn't penalize users who use them and are satisfied with them and at the same time encourages authors to make more frequent updates

Can you get them working in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile. Make sure you stay signed out of your sync account when testing.