Blocksite is still available as an Add-on, but is blocked once installed?

I've been using Blocksite as an add-on. Firefox has now disabled it for being unsigned. Blocksite is still available for download on the firefox site: https://addons.mozilla.org/en-US/firefox/addon/blocksite/?src=search Why can't I use this / why is it still able to be downloaded if it has become a problem? Basically, whats going on here? Even if I wanted to use a different website blocker, because blocksite is disabled, I no longer have access to the comprehensive list of websites that I've added to it. Thanks!