The breeders have to be the ones to do the right thing. It’s expected that buyers may not know, or care, about the standard. But breeders should have some moral obligation to the breeds themselves. Clearly many feel their obligation is to make money.
FWIW, Dachshunds are allowable in “merle” (correctly defined as dapple). You do see them from time to time, but the solid colors are more common.
As the Chis - they are supposed to be very small. 5-8" and not exceeding 6 lbs. Most pet Chis are too big, and 15-20 is a monster. It might still be purebred, just a horrible specimen.