That's certainly...interesting to say the least. My add-ons didn't break at all, but then again I wasn't using Firefox for the entire time allotted that they had a certification issue and were fixing it afterwards.
For me personally, I have used Firefox since the day I found out about the browser. I was attracted to it for some reason, don't remember why. I do know why I continue to use it however, because of their mission statement and the fact that they're committed to making privacy the number one priority. I was also super happy to see Firefox Quantum, showing their dedication to make the browsing experience better for everyone. Google Chrome, like rhombus has said has some major privacy issues.
Also, I HATE the fact that certain websites prevent you from using their services or accessing them unless you use a different browser (i.e Google Chrome).

But guess what... if you change your
browser user agent to the browser they want you to use, it actually works perfectly fine. And even if it truly had issues on certain browsers, just give people some kind of warning and let them proceed anyway. Google Chrome already has dominance over the internet market share, and it's going to get worse if developers only develop for the interest of one browser only. We don't want to go back to the days of Internet Explorer now, do we?
*UPDATE* - My add-ons did end up breaking due to that certificate issue you were talking about, but since there was already a fix out, I just downloaded the patch and everything was fixed momentarily.