My biggest problem with Civ (I got VI, played a bit, quickly lost interest) is that the ages run by way too fast relative to the pace of warfare.
I like Nubians, archers and production/gold bonuses are my jam. It's just too bad they have Slimer as a leader.
An eternal stick in my craw whenever I play Civ 6 is how fucking far they reached to find female leaders. 15 of the 42 leaders are female, and most of them are big stretches. Like if you write a short list of important French historical leaders and you pick two fairly obscure women over Napoleon and Louis XIV you should probably fucking kill yourself.
There's a lot of shit joke civs, especially Anglophone ones. Canada, Australia, Scotland. It really galls me that of all the Indian civs they could have added they went with the Cree (hunter-gatherers that accomplished nothing of note).
I too feel like I'd rather have the greatest/most iconic leaders of each civ be its representative, for the most part. The ones that come to my mind are:
Good picks they did:
Arabian: Saladin
Brazil: Pedro II
China: Qin Shi Huang
Egypt: Cleopatra; she may not be old school, pyramid Egypt, but there's way more personality to play with than if you go with Ramses
Gran Colombia: Simon Bolivar
Greek: Pericles
Hungarian: Matthias Corvinus
Incan: Pachacuti
Indian: Chandragupta is fine, but Ashoka works very well too
Macedonian: I don't know that this one really deserves to be a separate civ from Greece, though
Malian: Mansa Musa
Mongolian: Genghis Khan
Ottoman: Suleiman the Magnificent, but if they wanted a woman, they could have shoved it on Ottomans for Roxanna
Persian: Cyrus
Roman: Trajan and Caesar fit fine, there's lots of Romans a person could use that are all iconic
Scythian: Tomyris
Spanish: Philip II
Sumerian: Gilgamesh (really cool using a legendary figure for the oldest civ)
Zulu: Shaka
Changes I'd make:
British: Queen Elizabeth
Byzantium: Justinian (in fact, they have Theodora as an option... diversity, of course...)
Dutch: William of Orange
Ethiopia: Haile Selassie
French: Napoleon Bonaparte
Gauls: Vercingetorix (come on, why the fuck is Ambiorix the one?)
German: Otto von Bismarck
Japanese: Tokugawa Ieyasu or Emperor Meiji
Norwegian/Norse: Cnut/Canute. Harald Hardrada? Really? The loser? Or Ragnarr Lothbrok, go legendary like Gilgamesh
Polish: No clue but surely there's something better than Jadwiga
Portuguese: Henry the Navigator
Russian: I'd actually prefer Josef Stalin for Russia.
Swedish: Give me a fucking break. She's not even hot, it's an ugly tranny-looking bitch. It should be GUSTAV ADOLF YOU DEGENERATES
Ones I don't know enough about to even have an opinion:
Indonesian
Khmer
Kongolese
Korean
Mapucuhe
Mayan
Nubian
Phoenician
Vietnamese
Things that simply should not be civs:
Australia
Canada
Cree
Georgian (come on)
Maori - Why is this not just a Polynesian civ with Kamehameha as ruler? Why include the Maori specifically and not the actual KINGDOM of Hawaii?
Scottish
Things that should have been civs instead of the Cree:
Comanche
Cherokee
Iroquois
America is a hard one because Abraham Lincoln is far and away the most iconic, but I've also gotten completely sick of seeing him as a default leader in everything, especially seeing as he presided over the greatest self-destructive spaz out in the nation's history. I'm not enamored with Teddy Roosevelt either. I feel like Ronald Reagan would unironically be an absolutely fantastic civ leader, being a former Hollywood celebrity turned Cold War warrior. FDR, Woodrow Wilson, and George Washington are also all great choices. FDR is probably the smartest choice overall.