Yeah, useless a bit too far to generalize, you're right. But, in the end, it will won't be usable by general public or software hackers (in its original definition).

I don't have any Android devices, and I don't follow its forks, derivatives or general state too closely. If you have the money and the means, you can always make a fork of an open source software and make it work for you.

To be more accurate, maybe I can say it won't be very useful for the general public, but big companies can do whatever they want since they have the money and the man-hours.

Fire OS is a fully maintained fork, but it still requires proprietary blobs to be functional. As far as I know, there are no commercially-supported Android forks that have open-source drivers outside of the kernel.