u/smalg2, YES!! ! I have the same exact impression as you! My ER2XR also doesn't sound like the FR curves I found. "Muted", I'm not sure of, but Dark is definitely how I describe them.
However, as others have mentioned, their midrange is their strength, and I use them primarily when I want intimate vocals or quiet immersive instrumentals.
I do EQ a lot so I have a few profiles for them, but since the FR on internet is not helpful, I gotta do it mostly with my own ears.