Personally, Node.js+MongoDB is counter to my intended use cases. NoSQL databases are incompatible with my data models. Node.js has limitations in responsiveness, especially for complex (read: data/code-heavy) responses.
It simply doesn't meet my needs, and the community's focus is on improving areas that are completely orthogonal to my needs.
A native backend that is properly threaded and uses, e.g., continuations and thread pools to manage highly concurrent requests is far more preferable compared to Node.js, and proper support for RDBMS and memcached meets my needs better than MongoDB could ever dare dream.
It simply doesn't meet my needs, and the community's focus is on improving areas that are completely orthogonal to my needs.
A native backend that is properly threaded and uses, e.g., continuations and thread pools to manage highly concurrent requests is far more preferable compared to Node.js, and proper support for RDBMS and memcached meets my needs better than MongoDB could ever dare dream.