I can't stand how yellow it is even iPad Pro. If X is even more yellow than that...lol, screw that crap. I don't understand why Apple just don't let people adjust neutral color temperature manually, and the maybe make True Tone work off of that initial setting. They should realize this is an individual preference for people, much like the amount of brightness.
I mean, it's called TrueTone, so what you're asking for goes against the idea of the feature, which is accurate color reproduction regardless of ambient lighting conditions. When Tom's Hardware tested the display, they found it improved color accuracy:
Further testing also indicated that True Tone actually improves color accuracy. With the feature off, our iPhone X recorded a Delta-E score of 0.28. (Numbers closer to 0 are better.) With the True Tone on, that was improved to 0.21.
You can of course turn it off if you want, but Apple undermining the feature to accomodate what you think you perceive as the right color is not going to happen.