It's all perspective. If you remember when the TH-900s were released, the "best" closed headphones were not at the same caliber as they are today. The D7000s were considered one of the very best, but the TH-900s did in fact improve upon them by tightening up the bass and bringing out the really recessed treble a bit further (though I would still classify it as "recessed" on the TH-900s). The treble was one area that the TH-900s took a step back back as; to my ears, became even harsher and more strident. As mentioned, initially I could live with this, but as the months passed, this became more and more problematic for me to the point where they literally sat in a drawer for 9 months completely unused.
Back to perspective, since then the new 2016 version of the LCD-XC, Ether C and Ether C Flow and now the Z1Rs where released that all moved the bar higher to my ears. So based on these newly released headphones that all made listening to closed-back headphones pretty much as pleasurable as the very best open-backed headphones, my thoughts of the TH-900s were re-adjusted on where they stood in the larger scheme of things.