There are different types of "critical listening" for different purposes. In audiophile land, I think it is often meant to describe listening for shortcomings in the presentation of a system or given component. But it can also involve listening to compare different pressings of the same record, to evaluate their respective merits. In musicology, there are also different types of critical listening- one might be to analyze motifs or how it fits into the overall body of that composer's work, its influences, historical context, etc. Forensic musicology often involves picking out allegedly infringing phrases or elements and finding historical precedent for their common usage as building blocks by other authors. I think you need to provide context to afford more meaning to the term. To me, I most often associate it in home audio reproduction with listening to where a system or component reveals its shortcomings.
What exactly is critical listening? Who does it?
I'm supposed to listen to every single instrument within a mixture of instruments. And somehow evaluate every aspect of what I'm listening to and somehow all this is critical listening.
This is supposed to bring enjoyment?
I'm just listening for the Quality of what I'm listening to with all the instruments playing and how good they sound hopefully.
And I'm tired of answering that I'm not a robot all the time. That's being critical.