When did you most enjoy the music?

I still don’t pay attention to the equipment unless I am evaluating something. But I think you hit the mark with this:

Maybe it’s something that can’t be recaptured, as it is with a lot of things of youth.

Maybe it’s as simple as " Ignorance is bliss"  Life in my teens & twenties was about excitement. I woke up everyday feeling great and ready to conquer the world. Now I sometimes wake up feeling like I was run over while asleep. Now I spend my days maintaining my old body which bears the battle scars of my conquests. Hard to really get into music as much when I'm doing that. 

Yes, that 8 track in my 64 Impala sounded great. I still love music while I drive. But that excitement is not there today like it was when I was 20 something

Yeah, everything sounds awesome now, but it's never the same as it was back in the day when the friends were all and the world was new.

In the words of BB King, the thrill is gone, but the memories and appreciation are not. 

There is no comparison between the state of my audio system now with anything i listen to in the past...

Then i enjoy music the most now...

It is not the result of costly gear upgrade tough but mainly from acoustic room controls...

There is a big difference between music coming from an avarage uncontrolled audio system and music living in your room which dont seems to come from the speakers with a natural timbre...

Acoustic is the sleeping princess and the Queen....Any other things are the working 7 dwarves....

The general law is simple : because electronic design is mature now from decades ago any " relatively good system" will transform itself completely under the right acoustical controls.... Gear matter now less than room control....

There were moments in my youth that really stand out in my mind as well. Tubed counsel radio when I was 12, Early 60’s hearing the Beatles I Want to hold Your Hand for the first time (literally the first broadcast of the group in the US) on a plastic clock radio. Sears “portable stereo” with speakers removed and placed head in between. College several systems... drugs were involved. The ESS AMT 1D system I heard when buying a small bag of grass... he also had one of the most beautiful women (girl) as a girlfriend I have ever seen... guess that was a positive association..
All of those experiences were motivators to pursue high end audio and music. But I think they were circumstantial, emotional state when they happened. I think music, particularly when coupled with high hormones and associated emotional states create these marker memories and interests that we follow throughout our life.

Happily I don’t listen to my system any more, just the music. This is a fairly recent thing with my most recent upgrades. I find it difficult to listen to the system... it is so musical, I just get captivated by the music and do not listen to the soundstage or micro details. Come to think about it, increasingly over the last two decades I would upgrade as fast as posdible to get back to listening to music. My current system is incredibly good at establishing the emotional connection with me. It can work as a time machine given the right 1960’s or 70’s... or 50’ input. I can only think how much my young self would have loved the system I have.

Good question. It really made me think about what made the system I have today so compelling... it is that it has that emotional connection that I think I had been working so hard at creating for the last fifty years. I have finally done it.