Here’s a simple example to show why that’s not quite right.
- （彼が）ボールを落とした
- ボールが落ちた
- （彼に）ボールを落とされた
The first one uses the transitive verb 落とす, and means “(he) dropped the ball”.
The second one uses the intransitive verb 落ちる, and means “the ball fell”.
The third one uses the passive form of 落とす, and means “the ball was dropped (by him)”.
There’s an important distinction between the second and third sentences. In the second, the ball fell on its own, giving no indication of whether or not someone caused it to happen. In the third, it’s explicitly stated that the ball was dropped by someone or something, even if we don’t know by who or what.