Totally agree, Nokia had it in its hand to create a third option. Nokia had lots of consumer good will, the N900 (and Maemo) was super well received specially by developers but it could even compete against Android for normal consumers as well.
They should have iterated on this with every flagship phone and push it to the cheaper phones as well.
I was so sad and angry when this never came together. They just spiraled out of control after that.
OpenMoko - not really, it was major mismanagement in other areas (and some poor luck) that killed it, but AFAIR production volume was actually being predicted quite well.
Firefox OS, Ubuntu Edge - sure.