In a terrific podcast, Joel Spolsky and the StackExchange team talk about the failed communities they've tried to create.
There was a community for freelancers whose discussions revolved solely around how to get jobs.
There was a community for AI professionals without any AI professionals.
There was a community about gadgets which couldn't generate interesting discussion because the topic was too broad.
Providing subtle influence (leadership) in these situations is important.
You might need to initiate new discussions and ensure they appear higher than the same discussions repeated for the 20th time.
You might need to actively recruit the right people to the community and provide activities for them to participate in.
You might need to focus your community on a more specific area than the broader topic.
The problem is we don't differentiate between changes the community needs and changes the brand wants. For example, if discussions are repetitive it's beneficial to the community to subtly broaden the topics being discussed, as per the example above.
However, it's not usually beneficial to the community to get members talking about your products, or giving feedback or telling their friends.
Two thoughts then. First, don't be afraid to identify fundamental community problems and provide leadership. Two, don't confuse what the brand wants with what is beneficial to the community.