$229 at Massdrop. No mention of the amp used to test or how notoriously hard it is to drive T50RP IIIs correctly? Barely any mention of how moddable the T50 line is or how many other variants there are like the Argon or Mayflower?
I can virtually guarantee that the reviewer did not hear these headphones anywhere close to their potential, based on the photo that shows it plugged directly into a laptop computer. First, these headphones highly benefit from a dedicated headphone amplifier simply to achieve satisfactory volume, as volume levels will be anemic out of nearly any source. The "Low sound at max volume" complaint would have been rectified with a dedicated headphone amp. Second, nothing less than lossless music will sound good on any decent set of headphones. For the ideal listening experience, it should be in lossless via Tidal, FLAC, or an optical disc (CD, SACD, DVD, etc). Third, these headphones will also highly benefit from an external DAC such as a Schiit Modi at a minimum, or another transport/DAC with better audio fidelity than a laptop computer.
"No mobile-friendly features" is an odd complaint for these headphones. The Fostex T50rp MK3 headphones, which the Dekoni Blue are based on, were not made to be typical mass-market consumerist headphones, and so weren't made to have consumerist features. The Fostex website says that they were intended to be used as "monitor headphones by professional recording studios," so by implication, these headphones are targeted for music playback on dedicated systems, and not smartphones at all.