Comment 58 for bug 1653351

In practice it is so. Normal users will not be able to install the extension. Even advanced users, such as myself, will not usually want to force installation. I just wouldn't trust it anymore. At the very least it takes extra time to research its actual status, and you have to know or suspect in advance that it would work fine. And there is the risk that it will stop in the future without any warning, or worse, causing trouble to the Thunderbird you rely on for your important e-mail communications. Not worth it for most of us.