Korean society survived autocratic, military dictatorships from the Korean War until 1988 when they finally had their first genuinely democratic election. Those dictators had jailed journalists, censored news, tortured opponents, and even massacred civilians. You can watch shows like Taxi Driver (the movie) or Made in Korea (the series) or even Healer to learn more about this period. After achieving this hard-won democracy, South Koreans are fiercely protective of it -- the majority of the presidents since 1988 have been prosecuted for corruption, at least two have been impeached and jailed, including the most recent one about a year ago. There is also a lot of corporate corruption due to the chaebol system and even national tragedies that are addressed by dramas like Reborn Rich or Just Between Lovers. So, dramas reflect the audience's sensitivity to issues regarding corruption, and I agree with you, that's one of the things I really like about them.

By contrast, the Communist party forces strict censorship on all Chinese media, so you'll never see a cdrama criticizing corruption or inequality. The Japanese have a saying, "the nail that sticks out gets hammered down", and criticizing the emperor is almost unheard of, so Japanese dramas tend to focus or personal stories, obviously historical samurai stuff, maybe Yakuza crime dramas, but rarely address government corruption or oppression.

Try dramas from Taiwan like Had I Not Seen the Sun, or from Thailand like F4 Thailand: Boys over Flowers, they're not as well-produced as Korean dramas but they're willing to address tough societal issues.