I'm fine as long as they are still iconic and consensual cultural/political figures.
But if it's a controversial character who was just a military officer, for instance, it's not ok at all. For instance, Joan of Arc leading France would get me seriously triggered. I also dislike Mao for China, Stalin for Russia or Napoléon for France (yeah I don't know why Firaxis kept picking leaders worshipped by the far right for France... at least we got De Gaulle, Louis XIV and Catherine de Médicis). Hitler for Germany would be shocking as well. Some other "monsters" are less instrumentalized, so they are more acceptable I guess (looking at you, Gengis). In other words, if everyone agree on the evil status of a "villain" leader, it's ok. But if it looks like it's supporting the views of some... questionable contemporary groups, I will avoid it.
I don't have any problem with the current or announced leaders for Civ6. I'm also ok with not picking the most iconic leaders for each country - it's also an occasion to discover new things, and if I want a history lesson it's not the right place anyway. That's why Gorgo doesn't bother me much, even if I would probably prefer one of the Lacaedemonian reformers (Lycurgus being the obvious choice). Sparta isn't just about Leonidas and the 300 at Thermopylae.
I'm even less bothered by Carthago, Hannibal is mainly famous in military history, while Dido is the most iconic cultural carthaginan character (many works were written after her). Civilization is going to have trouble picking one leader for any republic like Carthago (with two shuphets) anyway, so picking a "queen" makes sense, just like Rome never had a republican leader (even though Cicero would be great), but always emperors.
I also think that having a leader you can talk to is now a defining asset of the Civilization series. Without that, they are "just another 4X game" with little personality. When making references to Civ, you'll see it's mostly done by making fun of the rulers. It also helps keeping in mind that Civilization is absolutely NOT about actual history, and more a fun game with a historical theme (in the sense that you will never be able to emulate history in a civ game, contrarily to other games in the same genre that are more about alternate history).