You can become less available for one role and more present in another.

Reduced availability gets read as decline, as though attention were one quantity that rises or falls. Usually it has simply moved. Someone who stepped back from the committee may be giving those evenings to a grandchild, a garden, or their own health, and less in one place is not less overall.

If your own capacity is shifting, say where it went rather than only what you are dropping. When somebody else pulls back, ask what has their time now instead of assuming something has gone wrong.