Speaking from my experience of living in Hong Kong for years and making countless business trips to China

First, speaking from my personal experience and modest knowledge...
1. Traveling to China's first-tier cities (Beijing, Shanghai, Shenzhen, Guangzhou) is about the same difficulty level as traveling to Seoul or Tokyo.
→ The infrastructure is good. Although prices have risen a lot lately, transportation and food costs are still cheaper than in Korea. Public safety is also quite good. However, other than being big cities, they don't have much unique character.
2. There are many scenic spots and places that history buffs will go crazy for.
→ Perhaps because it is such a vast country, the "hardware" for tourism is excellent. Beyond Zhangjiajie, Huashan, Jiuzhaigou, Taihang Mountains, and Mount Tai, there are many hidden gems everywhere. In particular, Xinjiang and Inner Mongolia have many truly hidden tourist destinations.
3. If you can't speak Chinese, you will face endless difficulties.
→ To be honest, I think traveling is extremely difficult if you don't speak Chinese, unless you are in those first-tier cities. English is not widely understood. Since I lived there for a long time and can speak Chinese, I didn't have much trouble, but for those coming without Chinese skills... another country would be a hundred times better.
4. As everyone knows, the "software" is bottom-tier.
→ Compared to the actual economic development, the development of the people's social awareness is too slow. Very few countries possess such high-quality tourism hardware, but it feels like the lack of "software" ruins the whole experience.
5. (19) I do not recommend it for nightlife/entertainment.
→ Enjoying nightlife in China is not only more expensive than in Korea now, but if you get caught by the Public Security Bureau (PSB), you are in serious trouble. Looking at reviews from people who got caught, getting caught for prostitution in Korea is child's play in comparison. If you want to enjoy nightlife in the Sinosphere, go to Hong Kong or Macau. It is legal there. Also, there is a way to enjoy "short times" cheaply. In Chinese regional cities (I believe even in fairly large cities), there are places called "Urban Villages" (Chengzhongcun). If you go there, you might see women in revealing clothes soliciting, similar to how Cheongnyangni or Yeongdeungpo used to be in Korea. However, the warning signs written there are chilling. "Beware of AIDS..."
I understand that all sorts of STDs besides AIDS are actually present. I don't know the details of the massage parlor industry, but I heard it is quite cheap. I never even considered trying it. I'm terrified of STDs.
Anyway... China is a truly top-tier travel destination for those whose tastes align with it...
While it might be less extreme than traveling to India, it is a place where opinions will be very polarized.
Still... personally, I think it's better than India.