A content calendar is useful when it connects publishing to a real business goal. Start with the audience, the question they need answered and the next step that the content should support.
Plan a small number of durable themes, then adapt each one for the channels where your audience spends time. This keeps the message consistent while giving each format a clear purpose.
After publishing, look beyond page views. Search queries, engaged visits and enquiries can show whether the content is helping people move forward and where the next improvement belongs.