I like FF, don't get me wrong, but this is going to absolutely fucking destroy user trust in Mozilla. This kind of incompetence, on a browser scale, is breathtaking.
Sadly, I have to agree that this feels like a big blow to user trust.
User trust is not really just about respect or values; it definitely also includes things like performance and reliability. The average user, right now feeling powerless, might even feel anger towards Mozilla for this - after all, they already downloaded the extension, why would they all just stop working behind their backs? They don't understand what CAs are or why certificates expire. People don't frankly care what place your heart is in when they are angry about something. Perhaps people are being dramatic, but that's normal. People are pretty darn dramatic about Chrome, too.
Meanwhile... I use Firefox everywhere, and I've lost my password manager, adblocking, security-related extensions, etc. all in one go, and the only solutions I'm aware of involve disabling extension signing. Gotta admit, even though I will probably continue using Firefox after this, that it certainly is a bummer.