Software wasn't at fault, it was hardware. S60v5 started on the wrong foot, with no GPU acceleration which caused serious lag (after the wonderful OMAP 2420 devices what the hell was Nokia thinking), low amount of ROM, RAM, and minor crappy manufacturing that was the N97.

Furthermore, such hardware deficiencies killed off N-Gage. It was an amazing piece of software (it had an app store and game center way before Apple), it just lacked GPU acceleration (sucky software graphics).

N900 was a great start at getting back in the game, however Nokia failed to advertize and provide future updates which would improve Maemo 5. Instead, Nokia focused on future iterations. Why dump an OS which was well received, when you could just improve it and release devices. The community brought portrait hildon-desktop instead of Nokia, etc.

I repeat, Nokia has no idea what in the hell they want. Their current failure is only a result of their poor management.

EDIT: They couldn't even bring promised OVI Maps navigation to the N900.