Yes each individual Korean city does great, but you will have half or less the number of cities as the real top tier Civs and the raw production is low. The German capital will have more production in the year 1000BC than Korea will in 500 AD. Russia will have 4 times or more cities by that stage ( I have won a science victory with Russia in the year 600AD peacefully). Greece will have 800 culture a turn by 500 AD and will be working on democracy if he doesn't have it already. Australia will laugh at Korea's measly +3/4 Seowon bonus. Mansa Musa will have three times as many cities and will be working on purchasing whatever districts and buildings he wants with the 2,000+ gpt he is making. Korea is just not even close.
Almost no civ is actually handicapped at anything (except like, Mali) so most of them can literally play the exact same build order if they want to. Korea is extremely strong for the same reason AI Seondok is strong; they get bonuses that are not only very potent in the meta, but that arise from doing things you were going to do anyways. You were always going to build early campuses, and you were always going to improve
some tiles in your cities, and you were always going to possess governors - and korea has huge bonuses (cheap and power campus, three kingdoms boost to mines/farms, hwarang) on those things. It's the same reason many UUs that don't replace anything are godlike on paper but in practice fizzle - you have to go out of your way to make them. But a sword UU shines because you were going to make them anyways. Etc.
Japan V Germany is another example. Japan has a very high level of potential for its districts overall - perhaps better than anyone in aggregate - but they have to build a lot of districts to get there, and it takes time. Germany is obviously an extremely fast setup as soon as they tech to apprenticeship. Korea has great science and sets up extremely fast.
Why would Korea have less cities? Am I missing something here? And Mali having more cities is extremely unlikely due to the unit production malus which also applies to settlers. Are we even playing the same game here?...
Germany's hansa will by no means outweigh Korea's faster apprenticeship and industrialization timings... Actually, Germany belongs in C tier IMO...
I don't see why Korea would have less cities. You can program an identical build order into half the civs on the same start/seed and have the same empire, and
ceteris paribus Korea's will just be way ahead on research.
I generally agree with you although I don't think consigning every civ that isn't an ancient era beast to the trash heap is fair - after all, to win, you usually have to go through the other eras...
Germany's primary power surge is "mid game." Several civs are extremely strong when they get their mid game power surges - zulu and ottomans, for example. The tradeoff made between these civs and the early game economic civs like korea and greece is getting to the mid game bonuses faster (korea, greece) vs having a qualitatively superior mid game economy (Germany.) Even in a competitive sense, some civs are truly only effectively countered by an early rush because if they get going they are going to be a real pain to stop. People like Germany so much because once you're in the mid game you are such a production monster that you effectively have a bonus in
everything for the rest of the game. But as I said, the very best civs shine because they can play very flexible and still win because their bonuses are attached to crap you were going to do anyways. You can prepare to defend a rush and still improve a couple tiles around your half price seowon.
Also, a general aside: I think tier lists are fun because people have different views about how the game is played. If you see civ as a competition between the player and the turn timer to win as fast as you can, some civs will shine. If you see civ as a competition between the player and other civs, others rise to the top. Choosing Civ X to face off against a nubia that conquered a neighbor and has the luxes of two continents is a
completely different proposition than an Aztec that has done the same.