What exactly is critical listening? Who does it?

Critical listening means optimizing the setup and listening closely to what the system is doing.  I use it when evaluating changes.  Otherwise, I just turn it on and listen more casually to the music.  

If critical listening used as a tool makes my system better, then yes, it does bring some enjoyment.  

Listening critically also gets easier with time / experience for a few reasons. It takes time to build the experience of what a realistic presentation sounds like - tonally, spatially, and effortlessly. And the better one’s source material, room, system, and hearing (or at least awareness of their personal hearing capabilities) are, the easier it is to understand the performance of any of the variables listed so that we may be able to critique what is contributing to what, or what is falling short.

Yes, it can be truly exhausting at times if you overdo it, but it’s a journey, not a destination, and one that, should you choose to accept its mission, you should traverse at your own pace. The key to success lies in motivation and the means to improve the variables for further fulfillment / enjoyment. Once either of those start to wane, it’s time to take a step back and stop taking it so seriously, and just try to enjoy the music. If you can’t do that, you’ll at least either have the motivation to find the variable that needs improvement so you can find more fulfillment, or you just need a time out from listening to music for a while. 

Your question is surprising, given how many times I’ve seen you on the forum. You express a common misconception about critical listening. It’s not about habitually listening in a way that is always dissecting every single instrument or constantly evaluating every sonic aspect. That would indeed be exhausting and detract from enjoyment.

Critical listening is best understood as "listening with a specific, often temporary, goal in mind for system improvement." Think of it like this:

Imagine your audio system is a garage. You don't reorganize it all the time; you do it when you need to. At the beginning; when you've added a lot more stuff to it; when you've changed things around in it or have different priorities. You don't reorganize a garage most of the time. You just use it for other purposes.

Same with an audio system: sometimes, you need to "critically listen" to set it up  or re-organize it. You might focus on a particular section (e.g., the bass response), identify what’s out of place (e.g., boomy bass), and make adjustments (e.g., move the subwoofer). This is a focused task with an end goal: a better-organized garage.

Once your "garage" (your audio system) is optimized to your satisfaction – perhaps the bass is now tight and well-defined, or the vocals are clear and present – you don’t need to keep "re-organizing" it. You simply enjoy the improved space.

Who does critical listening? Well, anyone seeking to improve their audio experience. This could be audiophiles, audio engineers, or even casual listeners who notice something isn’t quite right and want to fix it.

Does it bring enjoyment? Some enjoy the process of analysis. Others -- it sounds like you -- find thinking analytically to be irritating or difficult and not pleasurable at all. To each their own. But in either case the *outcome* is a more satisfying listening experience. Once you’ve addressed the issues, you simply relax and enjoy the music without your brain nagging you about imperfections. It’s about getting to a point where the "quality of what you’re listening to" sounds good enough so you can stop being critical and just appreciate the music. 

majority of folks I have noticed audition gear and trade alot to other brands chasing that nirvana, I think its more hobby to them than to enjoy and listen.  I bought what I consider the best and I like to sit down and listen to the most accurate sound I can, imagine want imaging to be the best it can and I want voices and instruments to be as natural as possible, I look for resolution, dynamics and control

Critical listening is necessary if one is to progress, also necessary to have a knowledge base/listening encyclopedia in order to obtain a reference or references as a goal. I spent far larger percentage of listening time in critical listening mode to my systems and others in early years, decades. Over time as I've come closer to my goals, far less time spent in this mode, mostly I admire the sound if I do go into this mode. 

Critical listening mode shouldn't always be seen in a negative light, it is a necessary tool in the audiophile tool bag.