Personalising an entire community experience around individual interests sounds smart.
If a member can tag topics they like, you can ensure they see discussions/content solely related to those topics. In theory, that keeps the member as engaged as possible.
The problem is communities are built around shared experiences. If everyone has their own experience, there's is no sense of collective experience. The community is not experiencing the same thing at the same time. That's an important factor in establishing both a sense of community and overcoming coordination problem.
A coordination problem, as popularised in Rational Ritual, is the idea that people take action if they know others will also take action.
I might go the bar if I know my friends will be there. However, my friends will only go if they think each other (and myself) will be there.
Hence, I need to know that they know that I (and each other) will go. And the same with them..etc…
Coordination problems are usually solved by everyone experiencing the same thing at the same time. This might well be why, given the choice, we're naturally inclined to sit in circles. Everyone can see that everyone else is experiencing the same thing at the same time.
Communities need to have shared experience. Have sub-groups if you like, guide members to those sub-groups, but within those sub-groups everyone must share the same experience. Everyone must know that everyone else is also sharing that experience.