As a testament to how your eyes adjust over time and how there's an adjustment period - I'm now a week+ in with my latest 12 (and no I didn't replace because of the screen). I've had it as my daily driver with my Xr close by for the occasional comparison. The Xr is, as previously discussed, noticeably cooler, with the whites seemingly a more "pure" white.
Within the last couple of days I've noticed a change. When I pull out my Xr, suddenly it doesn't look better any more, it looks more pink and less accurate than it did the first few days when my eyes thought it was whiter and more accurate than the 12. Now the 12's whites look better, even when True Tone is kicking in hard. And I can assure you, nothing magical happened to either screen in that timeframe.
I know the original problem mentioned here had to do with it being yellow with True Tone off, but a lot of the comments here are just about the general warmth and "yellow" feel of the, IMO, overly aggressive True Tone tuning. I disliked it compared to my Xr at first (and compared other OLED screens I've had). But suddenly, and magically, my eyes see the 12 as the more accurate and better calibrated screen when I compare the two...