I don't get why people say this / focus on Africa in this conversation. I've never thought Africa was small and was taught about the Berlin Conference, etc in school.

All the large continents are near the equator and hence the relative size of Africa, Australia, North/South America, Asia is not affected much by the projection. Antarctica is big too, even though wildly exaggerated by Mercator.

If anything, it makes more sense to say people don't realize how small UK/Europe is.