First of all: under the mentor system, mentors are a rather scary group, and they are very selfish. Don't think that high-level intellectuals are all kind, in fact, a large part of them will squeeze you more than the bosses. They rarely feel sorry for the students, thinking that you owe them when you come to study for a PhD, and they will desperately make you pay for them, because they will squeeze the results you have achieved, and it will be the benefit of their application projects and funds, and they will squeeze you without mercy.
Second: Academic research, especially at the doctoral level, is entering a completely new field. When I was an undergraduate, I was able to ask the dean to learn about many courses and write assignmentsWhen I was a graduate student, I could look up materials online and make some citations. But at the PhD level, there are very few people to learn from, and the supervisor will not help. The mentor says they're guiding you, but they're really just asking you to do your research in the direction of their project, which they don't necessarily understand. At this point, you will feel very lost, and even if a lot of money and effort is spent, what you write may have weak academic value. At this time, it is common to extend your studies, but once you graduate, you will find yourself in your 30s.
And finally: disconnection and difficulties in employment. After graduating, I found that I was 30 years old, only to find that the academic atmosphere and social disconnect in the school were serious. In society, I saw my peers driving BMW Mercedes Benz with children, and I couldn't even afford to buy a car worth 100,000. Don't say that doctors don't pursue material comforts, and the university professors I know are all for money. Times have changed, and no matter how good your reputation is, you can't use it. Furthermore, when it comes to employment, you will find that the people you compete with may be PhDs who have returned from studying abroad, have the same or even better qualifications as you (because they graduated from a higher-ranked school), and more importantly, they are in good spirits, while you may already look old.
All of this costs you time, energy, money, physical and mental health, and the most precious time of your life. Eventually, you may have to change careers and pursue a training career, or enter some businesses, or even choose a civil service position for a stable job. And these jobs, probably performed by undergraduates, did not waste more than 8 years of their time. Basically, it's certain that they're likely to be selected and transferred to the rank of deputy bureau chief before you, while you will be at best a deputy section leader and may not even have actual power.
So, what do you get out of doing a PhD?Vision?Vision?Knowledge?Knowledge sharing