I use an analogy as an illustration. I shoot a lot of photos, previously even for Nat Geo. Sometimes I use modern high-end lenses for high sharpness, corrected aberrations and soft background blur. Sometimes I use vintage classic glass for smooth focus transitions, swirly artistic background and soft compression of contrast. You can see combining both renderings also as a trend in most Netflix series.
Why? Because sometimes we need reference quality for certain purposes or occasions, to highlight something this way. But often we prefer something not reference level yet much more pleasing to highlight certain emotions.
Basically these are different tools for different occasions, they are not mutually exclusive, they are complementary.
Well, that is the case with daps and dacs that measure objectively transparent and with those that objectively are not transparent yet subjectively provide a sound that brings more emotions due to certain psycho-acoustic effects (more body, softer edges, wider stage) of their distortions and uneven frequency response.
I am grateful that we have both.
For desktop there are r2r made at a reference level which honestly don't sound much different from reference sigma-delta, and there are r2r with tge typical "euphonic" shortcomings that make them pleasant ti listen to.
As to the RU6, I have top level dongles measuring absolutely transparent, check asr review of Tanchjim Space, wonderful results. You know what, when I compare them the I always prefer the RU6 that objectively can't play transparently even 16 bit 44.1 khz Red book material, not to mention "high res".
(There is a tool in the shed that combines the pros of both for me personally and that's the Cayin N7.)