But in the past the core team have rarely acknowledged any community effort and weren't remotely interested in interacting with them or listening to suggestions. That hasn't fostered an atmosphere that encourages people to pitch in.
I would have to disagree with this. Both the Nano wallet and the NEM library/sdk efforts were started by the community. The responsible developers were rewarded with jobs in the NEM foundation and continue to contribute positively to the ecosystem. There is also that whole community fund thing.
As far as I know, people interested in interacting have generally been engaged. The NEM foundation has a whole team for this purpose. Maybe you know of some counterexamples?