You'll frequently hear people express 'night and day' differences, *astounding* changes in detail, 'huge step up in quality' etc.
Translated to English, this means subtle differences, nuances and relatively small improvements for the most part. There is a tendency in Hi-Fi to overstate things. Differences in Amps and DACs are a much more subtle thing than 'phones provided the amps are decently designed in the first place. There are differences and sometimes they are more obvious than others but at a cursory listen they may not be what a novice is expecting from the hyperbole.
Changing amps is not like changing headphones where the differences really are massively obvious, and even then most are not sure what these differences mean. 'It sounds better' springs to mind as a common vocalization. What sounds different is harder for most to nail down without familiarity with the terminology and experience.
You aren't deaf, you are probably not an idiot
, you simply aren't hearing what you were led to expect. Don't feel bad, we all become a little disillusioned from time to time. Knowing what you're hearing and how you're hearing it may be as simple as your prior statement of certain tracks becoming annoying. You may be hearing what a crappy recording you have for the first time. That's a big difference right there showing the amp/dac to be more detailed and revealing than your old gear, not a good thing for you I admit, having your music to be reproduced, warts and all, as not so great but it's there and you are now aware of it.
This is what good gear does, it totally screws a lot of music for you as you find out they did a ****ty job recording it. Such is life. Find a good recording of something and it'll make you grin from ear to ear.
Give it time, learn to appreciate the subtleties in recordings and allow your brain to assimilate the new level of listening.
PS, I keep gear around that can make most crappy recordings sound at least listenable when they would otherwise be a total loss on much of my other gear. Many find the Stax 003 to be dull and rolled off at the top end, but it works very well on overly bright Japanese recordings which are downright painful on my AKG K1000.