This is absolutely not true at all. In physical painting you do not have a colour wheel were you pick colours to slap on. You can create a wash of colours and hues just with Zorn palette. We are taught to use fairly limited palette in oil painting even today, although you can in principle buy every known hue and slap it on - but that is not painting and that won’t produce anything worth the canvas it is painted on.

You don’t need to believe me. Look at Egyptian sculptures that have survived fairly well in the tombs. Or Greek and Roman paintings, some of which have survived quite well and shown in the original article. I spent 3,5h cgoing through the collections of The Archeological Museum of Napoli, and there’s plenty of them. They used muted earth tones like most skilled modern painters would.