Measuring engagement then becomes one piece of data that's valuable, but shouldn't be the only piece. When engagement data is combined with qualitative community surveys, enthusiasm from members to contribute to a community, clear and timely responsiveness to community needs, membership growth over time and geographies, depth of member interactions (whether across community channels or within specific channels), what's topically important to members and why, and overall sentiment and change in sentiment over time - that's when community builders can begin to better understand the health of their communities and their impact on their business.
Engagement is an important piece, but just one of the pieces, that helps paint the full picture.
Disclaimer: I’m a co-founder of Common Room [1] and a we’ve invested a lot of energy in solving for this exact problem. You’re welcome to check out the product (it’s free to sign up) and would love to hear of ideas or feedback.