Decline or shrink a meeting politely

An invite arrives that should be 15 minutes, three people, or an email.

Help me respond to this meeting invitation.

1. Judge what the meeting actually needs: my attendance, a shorter slot, fewer people, or no meeting at all. Give one recommendation, not options.
2. If I should not attend: draft a reply under 50 words that declines, says why in one clause, offers what I will do instead (send input, read the notes, nominate someone), and keeps the goodwill.
3. If it should be shorter or smaller: draft the reply that proposes that, framed around the outcome rather than around my calendar.
4. If it should be async: draft the message suggesting the alternative and the specific format it would take.
5. Tell me honestly if this is one I should just attend.

The invitation and my context:

Fewer meetings. Declining, shrinking or replacing a meeting that does not earn the hour.