People act by means of instruments and causes: they write with a hand, walk with feet, and speak with a tongue. The presence of these means does not make them independent originators of existence.
A means or cause is a condition or pathway associated with the occurrence of an act; an instrument is the immediate medium used; creation in the strict sense concerns bringing that act into existence. These roles are distinct.
The disagreement with the Muʿtazilah does not deny that human action visibly proceeds through human capacities. It denies that such capacities are independent creators outside divine origination.