I understand the anxiety about 20th Century leaders. Because that will always bring up discussions about you-know-who. But then again this franchise has used a lot of leaders that weren't exactly angels themselves. But even if the Charlie Chaplin look-alike remains off limits. There are plenty of 20th century leaders worth exploring. A charasmatic leader like Castro seems tailor-made for the Civ franchise. We gotta get the Beard in this somehow. America and Russia should have Cold War leaders. My pick would be Ike or JFK for America, Khruschev for Russia. The tension between those leaders reached epic levels. Why not bring that kind of drama to Civ.I'm in the group of those who prefer early era leaders, as they are more interesting, at least for me. At least they could be avoided when Civ offers more interesting earlier leaders, like Netherlands. However... if the game has recent technologies, recent buildings, recent units, recent wonders, then why not recent leaders as well? Look, I don't think the game should be full of 20th century leaders, but some of them, around half a dozen, I don't think would hurt. Not even Civ6 has many of them.
Also thinking about gameplay, recent leaders can interact with late game mechanics.