I disagree entirely with this, ACID only makes guarantees at the database level itself not the system as a whole; it's possible that using ACID in the database could render the system as a whole more vulnerable than not using it. Take for example MySQL/InnoDB which offers durability (the D in ACID). If you have a write heavy database you could end up in a situation where your server ends up stalling waiting for MySQL to commit the write to disk. In effect, your server ends up building a large buffer of queries to commit to MySQL and sits there waiting for MySQL to become available. If your server or system crashes, all of that data gets lost.

You may have been much better off, both performance and correctness, to relax MySQL's durability from flushing on every write, to flushing/committing every 1 second (using innodb_flush_log_at_trx_commit). Doing so improves performance by multiple orders of magnitude (it can be the order of 10-100x) to the point that your server is no longer sitting there queuing up queries for writes to complete. The database loses some guarantees about durability but the system as a whole gains better durability.

I could make similar arguments about the other properties as well, the point is that a competent person should actually know this stuff, understand it, not just memorize an acronym and boil the entire issue down to whether a database has ACID or not. It's not a binary matter, it's more of a continuum where each property can be tuned to various degrees. MySQL and Postgres both offer many options to tune the various ACID guarantees from having complete conformance to relaxing them with various upper bounds. Relaxing guarantees about a local property of the system can improve the guarantees of system as a whole.