Because if you spend enough time on the internet, especially the Western side, you start to hear voices of people who oppose their governments and not enough from those who support it.
Even many who are supportive tend to say that their government is authoritarian.
Are you not taught marxism-leninism in school? The books Luna Hoi is translating are some sort of school textbooks, right?
Definitely not in school. You only learn ML in public universities, and even then it's no way in-depth enough.
From what I remembered from my highschool. You are not to taught ML fundamentals untill you are in university. However, you are taught some socialist world views and some historical materialism in both civic and history classes. Most kids wouldn't pay attention to it since they have to focus on STEMS subjects for the university exam though 😞
In university you have to take classes in ML which will have affect on your grade so people do pay more attention to it. But unless you are major in it, most people would just forget about it after their classes to spend time doing what university students do. It's pretty much the equivalent to mandatory civic classes in the West.
At the end of the day, while the education system in Vietnam have a more nuance view on socialism and have actual communist content (instead of the usual anti communism trash in US textbook). Majority of the time, people are simply too occupied with other things to learn it in depth.