Unfortunately it was about cutting losses by that point. There have been thousands of video games that were completed but never released for various reasons ( Half-life on Sega Dreamcast for one ). But It's all to do with manufacture and advertising costs and projected returns. Plus in this case the manufacture of more figures would have been necessary too.
They knew consumers would jump ship when 'the announcement' was made, and it was just cheaper to cut their losses than continue production of a 'dead' franchise just to keep a few fanboys happy. Go in any store now and if you can find Dory or Nemo, they're next to the scant other figures left in stock which are heavily discounted to clear.
Also if we'd got Maona, we'd have then complained about not then getting whatever else was on the upcoming film schedule after that.
- It had to end somewhere, and we should just be grateful for the ride we had. As the consumers our buying habits drove the model, not our wishes or feelings. The money men at Disney never gave a monkeys about that. And to be honest even though the environments look beautiful in Moana, how much action and game transferable events are there in it? I would rather had a much improved and detailed play-set based on Incredibles 2, Cars 3 or something more action based