This is an effect of total boosting everything. Yes, unlocking new policies is fun, discovering techs is fun, but right now all buildings provide os much yield and players are snowballing so hard, it jumped the shark I believe. You go for culture win - you usually just have to wait for ideologies to open, you go for science, you know 50-80 turns earlier you won and just have to grind that Apollo. Domination? At certain point if you made proper policy/religion choices, each city conquered makes you stronger.
And that hurts so many civs, who have late UU. People are ranting against England recently, but ManOWar opportunity window is quite tiny and difference is not that noticeable when everyone has huge army. Same goes for Musketeers, Carolean, Melah Sefari (or whatever Ethiopia UU is named), Minuteman and so on.
Thats why Pictish warriors, Immortals and Legions or Jaguars are so strong. Early on, your UU is like 50% of your army, later on, it's just few additional units. Three Pitcish warriors can wreak havoc and get you religion. Try doing that with Three Musketeers (pun intended

). Ok, I highjacked topic. My point was - Korea is fine. And if they get nerfhammered, there are plenty of other civs in line first (hello Aztecs).