I’m just as annoyed by the overuse of the Mercator projection as the next guy, but no, I don’t think we can blame it in this particular instance. Consider the similar case of a day/night map, which pretty clearly reads as 50/50 even when it’s Mercator:
(Upon further scrutiny comparing these two maps, I think the missing Antarctica might be a factor too.)
I’m just as annoyed by the overuse of the Mercator projection as the next guy, but no, I don’t think we can blame it in this particular instance. Consider the similar case of a day/night map, which pretty clearly reads as 50/50 even when it’s Mercator:
(Upon further scrutiny comparing these two maps, I think the missing Antarctica might be a factor too.)
Also, relevant XKCD.
That day/night map is not Mercator though
(Nor is the map in OP)
My argument applies to any cylindrical projection.