I cannot see how you think it is that simple when there is still no agreement to what is the ideal digital filter co-efficients in term of linear and minimum phase;
Because at this point, we're talking about fidelity to recordings vs audiophile terms like "musicality," that can mean almost anything the individual audiophile imagines they mean, not the performance of DACs.
my current DAC actually sounds warmer and more analogue-rich than another DAC I heard and yet measures better, for me it is a bit of a head scratcher.
If you're talking about warm recordings, that doesn't surprise me at all. What would surprise me is a DAC that measures extremely well, yet renders all recordings with the same kind of warmth and/or detail; then I would question the measurements.
If you heard the system you would say the CD player-DAC is colouring the system, but measurements would tell you otherwise.
No, I wouldn't, because I'd be listening to the system, not the CD player. If I wanted to ascertain your system's neutrality without comprehensive measurements of every component in the signal chain (and a trusted engineer on hand to help me interpret them

), I would listen to a variety of recordings I'm very familiar with, noting how it renders the known differences between those recordings and watching out for any systematic sound or character that cut across all recordings. And if I heard one, frankly, I would begin with the most likely offender - the speakers. If I wanted to evaluate a DAC for neutrality, I would put one in the chain that I know is of high quality, built with the goal of the highest levels of fidelity, and switch the DAC under evaluation in and out. If your CD player added a consistent character to all recordings, or sounded "warm" compared to the reference DAC, then I would think it is coloring the system.
None of this, by the way, is right or wrong. The right thing to do is build a system that pleases you and enjoy listening to music. If it rounds the edges off of 70s rock recordings (that probably need that), and softens Cannonball & Coltrane (which doesn't need it) and it still pleases you, good. Enjoy. But stick to "warm" and "musical." Neutral, transparent and accurate have real meaning in this context.
Tim