Right. What you want is horrifically insecure, which is why everyone is moving to disallow it. Chrome beat Firefox to the punch, but this change has been desperately needed for a long time. As long as you have a product used by millions of users, it's a giant blinking target for malware. Signing is entirely about being able to pull that malware out of the field after it is discovered -- and there's some really skanky add-on based malware out there.
As has been mentioned, if you don't like it, you have options -- unbranded builds and ESR releases let you do exactly what you want to do. And, again, that's far more than you can say for Chrome.
So, really, your complaint resolves to "Firefox will now be secure by default when it comes to add-ons, and I'll have to go through the inhumane and grueling task of downloading my Firefox from a different location on the web if I want to keep doing what I'm doing." That's a little hard to take seriously.