The problem with my position is that countries like Sweden and Georgia are in the game. I know a bit about Byzantine history, and even then, Georgia is a small player. Sweden had its 15 moments of fame and has done little else other than invent dynamite since. I have no idea why these countries are in the game.
Well, the main reason that Georgia is in the game is probably the Tamar's meme, maybe Firaxis wouldn't consider it if it was not the meme. Even so, I think Georgia is a good inclusion (boring gameplay, but cool addition). The Caucasus was never represented in the game before with a playable civ and Georgia made it. Obvisiously Armenia could be a better option, but would be controversial, so Georgia is probably the best option if we want Caucasus represented in the game.
And Sweden is in the game because of its gameplay in mixing culture, great people, diplomacy and giving new world competitions to scientific and cultural awards (Nobel Prize) as Sweden is the best civs for such gameplay, in addition to giving a post-vinking representation to Scandinavia. I don't see Sweden as an unnecessary inclusion.
That is why I don't like this argument that a small population or size should exclude civs, it's quite simplistic.
Possibly, some people have resistance to smaller cultures and civs from other places that they're not familiar with because they're not used to seeing this in Civ. Until Civ4 only large civs were included in the game, in Civ5 we had a little more diversity adding Sweden, Morocco, Brazil, Polynesia (although not a fan of the blob) and in Civ6 we had a very diverse game both in playable civs and in city-states representing cultures from around the world quite well. Perhaps adding these civs to the game will make people who are unfamiliar get educated and see that history is more than the European wars that we are tired of seeing in history books.
For example, I had never heard of Cree before R&F, and after playing and getting to know their history, I find them fascinating. I had heard of Maori on the surface, but now knowing more about their history and culture, I already think they should be in all editions of the game.
Anyone can look at Mapuche and think it is a random tribe, but today they are possibly one of the largest native nations on the American continent and were able to resist the Incas and Spaniards for centuries.
I know that is coolest to play with big empires of the history: Mongol, China, England, Spain...but history is not only of the biggest ones. And adding small civs don't mean exclude the big ones. If you look at the game you'll see that most of the big empires are already in the game, the biggest one missing is Portugal, which is probably coming in March.
Some civs can be interesting if they have a nice culture and history, a nice leader, a good opportunity to give a nice and unique gameplay...