Have you had your hearing checked by an audiologist. I know I have hearing loss and have an appointment next week. Still I can readily hear differenced in DACs.
I have found the more I invest in AC and electrical noise control the easier it is to hear the DAC's sound. The first thing I notice is the fullness and clarity of the low end. After that I hear the separation of notes and instruments. And then timbre and tone.
I have settled on a balanced DAC with a good tube DHT output stage. I am looking for a relaxing sound. Along the way I have learned to recognize the fatiguing digital characteristics of DACs with jitter issues.
I will say 5 years ago I could hear differences in DACs but maybe couldn't readily tell which I preferred. I would listen to one DAC for a few weeks then change to another for a few weeks. Eventually after getting over chasing the shiny stuff like low end clarity or soundstage or midrange presence and holography I would find I just liked listening to one DAC over the other because it was more relaxing/engaging.
As I moved up the DAC ladder price-wise I got more of the shiny stuff and more engagement at the same time. However, I am not sure I would appreciate a lot of the differences without the level of AC noise control conditioning I have.
I have found with each addition of noise control the performance of my system improves readily and changes in gear becomes easier to hear.