How are you hearing no difference?

In fact, in the case of power amplifiers as an example; it needs to accurately amplify the input signal, and transfer that signal, fully intact, to a low impedance load.
A well-designed power amplifier, in theory, is not supposed to reshape the input in any unintended or involuntary manner, so I support the concept that accuracy improves when the potential for error and distortion is minimized. 

Hence there are indeed, subjective differences in DAC,s and particularly pre/ power amps - however: much depends on how they integrate with the speaker load and the components having low errors and distortion.
see: https://www.thesoundadvocate.com/2018/10/the-role-of-power-amplifiers-today/

Unfortunately, there are many people who’ve never been taught how to listen or what to listen for and that’s because they’ve never met a person, or found a dealer/store, who was willing or able to teach them.  Can you tell the difference between a male and female voice?  Congratulations, you can hear.  If you go to a Hifi shop to listen with the preconceived notion you won’t hear any differences, then there’s a great chance you won’t.  The teacher has to be willing to teach, but the student also has to be willing to learn...  

Bingo! 

I need a psychologist to weigh in here. (I am not one). The central fallacy as I see it is; assuming one can hear a difference in presentation between two similar components, is one better? Chocolate and vanilla are both ice creams, both cold and sweet, but decidedly different; so which is "better"? Can't they just be different? I prefer vanilla, so to ME it is "better."
This is the tyrrany of choice; we assume that because two things are demonstrably different one has to be better. Take tubes and transistors. They both distort, but in different ways. This is what gives them their characteristic "sounds." But as they improve in quality their distortions minimize and their sounds become more similar. Still, each has a distinctive "sound" of its own; perhaps a vanishingly small difference but since there are two different pieces being compared then at least a theoretical difference. Which is better? The one I prefer may not be what you prefer, but for me the better component is the one I prefer, and I don't really care what YOU like best. 
I find audiophiles divide into two groups; those that listen to music with components vs. those that listen to components with music. 

The problem is too many people make this way harder than it has to be. A lot of people listen for a lot of different things.  For me it’s simple - I listen for clarity/resolution/detail - basically, do I hear things I’ve never picked up or heard before and is it more intelligible?   So to dohanian’s point, chocolate vs vanilla = Speakers are the instrument - do you want a Taylor, Martin, Gibson etc. guitar?  Find the speaker that tonally appeals to you.  Now, who do you want playing your instrument - your Electronics?  If you liked the Taylor guitar and handed that same guitar to Jeff Beck, Eric Clapton, and Chet Atkins, it’s going to sound very different, but for one of those guys, that guitar is just going sound right with them playing it.  So tubes, or solid state?  Yes!  One will be more right and “Does it get out of the way” - or does it add or take away from what you’ve heard in that recording you’ve listened to a 1000 times?  There in lies your answer - yes it’s better or no it’s not - because it certainly will without a doubt be different one way or another, however, different doesn’t always mean better or worse, but like I said, there is a synergy that can happen with Electronics and Speakers that can just be great and then you should know.  That’s also why it’s important to pick well recorded music to audition with because then understanding flaws in recordings of music you truly like to listen to becomes easier to discern.  The Music has been mixed, mastered. EQ’d, engineered and produced, so the better your Electronics/Speakers are, the more they show differences in those recordings - you’re never Improving the signal with anything, you’ only making it less bad and I think once everyone understands that, then the differences between good and bad become a lot clearer!