It’s most definitely not “meaningless”. Your point is a semi fair one if you’re talking objective data; however, we have a general reference point and neutral space to refer to.
If you want to continue to be obtuse, you can use the same colorspace/LUT that any generic phone camera is tuned to.
You may download Filmbox Lite for free and compare it in any way you wish. We have an opinion on it based on our deep understanding of this subject matter.
That's exactly how it works. Take your source digital image/video, run it through a neutral DCI-P3 output LUT and you have exactly what people are asking for as a "before" video.
Pretending image mastering and color correction is incomprehensible doesn't make it so.