Yes, you are wrong. For example, the "I" in ACID stands for isolation, which offers some guarantees regarding concurrently running transactions. In particular,

Yes, you are wrong. For example, the "I" in ACID stands for isolation, which offers some guarantees regarding concurrently running transactions. In particular, if you have 2 concurrently running transactions A and B, and A finishes before B, and B fails, then the database does not return to the pre-transaction state (if failing transaction B would cause transaction A to be rollbacked, the Isolation principle would be violated). Furthermore, many real-world databases do not fully provide ACID guarantees, and yet you can reason about the database anyway.