It has been rubbish from day one, and it is still so.
Down-Them-all was the one thing which ensure my continuous use of FF, but you have really missed the bus on this one - as well as the other add-ons which you have killed off willy-nilly.
There is NO incentive to keep using this new version - you have shot yourself in the foot..
*****
And now some - probably - 6 months later, and it still is rubbish, and Firefox still seems totally disinterested in creating their own downloader on par with DownThemAll.
Seems I've been backing the wrong horse all these years, you are no different from the other corporate software houses.