I agree. My first thought when reading the article was "WTF? No encryption?". Would be interested in learning more about the company that makes these, and how something so obvious was not done.
Why it hasn't been fixed since is shocking!
Well, to be more accurate, I believe what you're saying, but I don't believe that it is a valid excuse.
Most of the functionality of these drones could be duplicated with nearly off-the-shelf hardware. (at least off-the-shelf for Boeing/Lockheed/General Dynamics/Raytheon/etc).
Not for the Russians it wasn't! Nor for the French, who will happily sell weapons to whoever wants them (as we Brits learnt in the Falklands War).