The engineering time lost rebasing everything on top of Qt because Nokia wanted a migration strategy from Symbian would seem to be massively larger than the time spent on reducing userspace wakeups (something that could probably be done in a few months by a single competent engineer). It's possible that their approach killed them, but when we're talking about dysfunctional management and massive political infighting between the Symbian and Meego teams it's a lot easier to just ascribe it to corporate ineptitude. We're talking about a company that refused to consider the iphone a threat because its camera had fewer megapixels than their latest Symbian device, even if said Symbian device was approximately unusable as a phone.
It's interesting to compare to Palm. Their kernel was pretty much stock (there's some additional drivers), and while they didn't take the effort to attempt to upstream stuff they'd probably have had little trouble in doing so. They ended up shipping a sufficiently attractive mobile OS that it achieved their goal of turning a failed company into an acquisition target. Which model were they closer to?