Total member count looks good on a slide and tells you almost nothing. These are the indicators that actually predict whether a community is healthy.
What to watch
Track active members (not signups), returning-visitor rate, posts per active member, time-to-first-action for new members, space participation spread, event attendance, and paid-tier retention. Together they tell you whether engagement is real and sustainable.
Watch the trend, not the absolute number. A smaller community with rising participation is in far better shape than a large one quietly going quiet.