Quick take
Zapier is useful when work is already repeatable but still being moved by hand. Think leads, forms, emails, CRM updates, Slack alerts, support tags, invoice steps, and content handoffs. It is weak when the process is vague. If the team cannot describe the trigger, the data, and the next action, Zapier will only automate confusion.
Best fit
Use Zapier when one app receives information and another app needs to act on it. The best workflows are boring, frequent, and easy to check.