It might not exactly be explicit racism, but the Civilization series, even with its newest entry, can be frightfully Eurocentric and lenient towards the terrible history of imperialism and colonialism.
A few random examples:
1) Describing an era of history for all civs as the "Renaissance" when the actual Renaissance was a purely European cultural movement. Proper term used for this age in actual history books is the Early Modern period. Having a middle ages as a universal era is similarly problematic.
2) Building the whole tech tree around the order technologies arrived in Europe. Similarly, the culture tree is built around European cultural shifts, going as far as having the Reformation be a universal cultural tech.
3) All kinds of problems with religions. It treats all religions like they are proselytizing and seeking to displace all other faiths, but many, including ones given as default choices are not. The portrayal of animistic/shamanistic faiths as culturally and technologically inferior is also an issue.
4) Civ 6's Colonial War Causus Belli is just gross. Every other Causus Belli is used to establish an idea of "moral and just" war, like liberating a city captured by an aggressive enemy, which gives you less diplomatic pressure for combat. Treating colonialism as if it were anything just is terrible. Even worse, it defines colonialism as the conquest of technologically inferior civs, which propagates the highly racist myth that Europe conquered the world due to Europeans' superior intelligence and culture, and that Europeans brought civilization to the rest of the world. In truth, colonial conquests came about due to opportunism and brutality, no different than any other conquest.
6) I could say a lot about how they choose civs, but a big one is the discrepency in how it names and portrays civs. White and European civs use the names of modern countries and more often use more recent leaders. Darker skinned civs from other regions are more likely to use antiquated cultural names and be portrayed as more primitive. If Montezuma were treated the same as Europeans, his Civ would be called Mexico, not Aztec. Similarly, his units should be upgraded swordsmen at the very least, rather than just warriors.