Religious Idols is a relatively useful pantheon for Nubia, and even more so for Mali. The extra Faith that they receive from Mines over luxury and bonus resources can be used to purchase buildings in their Sugubas, providing them with more Trade Routes and additional Gold that they can use to purchase units and buildings for their Holy Sites and other key districts.
That being said, these two civs are usually better off choosing Desert Folklore, which increases the yields of a greater number of (unimproved) tiles. For other civs, Stone Circles is usually a more efficient pantheon than Religious Idols, especially for players who aren't serial harvesters of all available Stone.
|Religions and Pantheons in Civilization VI|
City Patron Goddess • Dance of the Aurora • Desert Folklore • Divine Spark • Earth Goddess • Fertility Rites • Fire Goddess • God of Craftsmen • God of Healing • God of the Forge • God of the Open Sky • God of the Sea • God of War • Goddess of Festivals • Goddess of the Harvest • Goddess of the Hunt • Initiation Rites • Lady of the Reeds and Marshes • Monument to the Gods • Oral Tradition • Religious Idols • River Goddess • Religious Settlements • Sacred Path • Stone Circles