What each one is built to own
A trigger-action tool is built around the event: when X happens, do Y, then Z. It is excellent at wiring two apps together with no code. An AI employee is built around the job: the whole piece of recurring work, including the parts that need judgment — matching columns that are not in the same order, applying this month's pay period instead of the calendar month, deciding which exception is worth escalating. That judgment is usually the part a trigger chain cannot express.