[prmph]

Quality is the ratio of the value you derive from the software to the cost to you of using it.

Most typical quality attributes can be subsumed under this schema.

If the software costs too much to change because the architecture is poor, that reduces the quality.

If the interface is poor or it is slow unnecessarily, it costs you more time to use it, and that reduces its value to you and hence its quality.

If the software is insecure, you may actually lose privacy or even money using it.

If the software is not robust, you run the risk of losing data and time, etc. when using it