I don’t personal fancy DSD, and high-res or not depends on the recording. Many people like to upsample with something like HQPlayer and I’m quite sure I have read that you have recommended upsampling in a computer not long ago, lol. I don’t like to upsample in a computer, but nor will I criticize if others do.I've auditioned a few highly-regarded DACs in the last few years, and all the sigma-delta-based models sounded artificial to me to varying degrees. It is irritating to me that someone will then write that the DAC sounds best playing back DSD, or high-res. I'm firmly a supporter of the idea that since the majority of music is 44.1/16 that a DAC should be designed to play it best above all else. If a $100k dCS stack sounds best with 192k, then it is, arguably, a failure of the design.
One thing I noticed listening with the R2R 7 (and the other two, comparable DACs I have here) is how natural they sound listening with TIDAL, or anything I have in my library, regardless of sampling rate, to the point that I didn't think to write at all about the sound in detail, because they were so seamless and natural that there is nothing really to say. Unless I sit for hours and A/B piano notes or sections of tracks, simply put, all make me enjoy listening to the music and forget about the gear.
Failure of the design, I don’t know. If a recording is made in high-res with more real samples and more bits (IE more data) is it then not reasonable that this sound a bit better? What about MP3? A high res recording down mixed to 44.1 is not lossless just like a MP3 to 44.1.