They started disabling extensions installed by user on some websites without clear explanation why and when it will happen and intentionally hided settings to disable this functionality.

Should I read their own post again?

Why not ask user first? "Do you want to disable add-on not monitored by Mozilla on this specific site?".

Also, how many times users asks about this functionality? "I want Mozilla to monitor add-ons installed on my browser and disable it on some websites, when Mozilly want it" - surelly most of the users wants this.