It's the laws of both physics and physiology which constitute RGB into true additive color, and CMY into subtractive. Mixing apples with oranges in this respect (RYB) is just poor education, inherited from kindergarten finger painting classes it seems. After that, it's an extremely complicated problem of finding "ideal" dyes or pigments for particular applications, which of course don't really exist, so things need to be tweaked. For example, the older Ektachrome green reproduction was rather contaminated with magenta. Fuji cleaned up the problem long before Kodak did. But people tend to misinterpret visual reality for what they are photographically accustomed to. Early pigment prints generally used alizaron crimson, chromium oxide green, and cadmium yellow - and other than being rather efficient at poisoning the user,
was really a very poor set of process colors. Still, people made it work and some wonderful if rather unrealistic prints transpired from time to
time. Photographic color is never reality, even in the best of circumstances. But back to film - I personally switched over to the "green boxes" because with Fuji sheet film the green was so much easier to tame when printing Cibachrome. Not until Kodak came out with E100G did they have an equivalent product. And sheet Kodachrome was long long gone (though I did print 35mm and 120 Kodachrome, along with
old-style Agfachromes and numerous other things - each with its own "look").