Someone who's teaching you right now might never be able to join the job market anymore.

Let's keep this short. Some backgrounds:

• I have a career goal of becoming a Backend Developer, and I start with Frontend.
• I'm currently a 3rd year at FPT University.
• I am getting paid (minimum middle-class salary) as an Intern to work in a Frontend project.
• I'm 20. (at 2021)

So you want to be a Frontend Developer

• You need a Frontend framework. Your school only go so far as basic HTML & CSS (on Coursera, go figure). No JavaScript. So just with this first point alone, you can't get into the job market after 4 years of university.
• A professor teaching C# and C# Web Development doesn't know how to proficiently write JavaScript, let alone ES6 variant.
• They don't teach you Git. I doubt any one of them is knowledgeable enough to teach Git.

Well, at least they're teaching Java, C# and SQL Server for doing Backend works, right?

They only produce Backend developers! - you said

• Nobody teaches you API stuff. REST API, GraphQL, it's non-existent.
• To be a Backend Developer is no easy feat. Look at the backend roadmap down to the near bottom, that's where the Junior Backend guy is. Doubt? I am a living proof of having worked with a Junior Backend guy.
• Backend is like a dangerous world. If your data is gone or leaked, your company is gone. If your server goes down for 30 seconds, for example the server of an eCommerce website, and they can't place an order, they would probably never come back.
• No one hires a freshly graduated student to work in Backend. Try to find a Junior Backend job that a graduate can work in. With Frontend, I can probably just try my luck on a Junior Frontend interview right now and no one's complaining.

What about Business Analyst?

I don't know. You could try, but you will probably end up at a Fresher position and learn another year. I can't say the things they teach at FPT is beneficial to your job, all I can say is that what I'm doing at work is far from what I think I'd do.

You really have to learn the hard way, and at scale.

So what? Afterall, I am a Fresher now. - you said

You really think that it takes 4 years for a person to be able to work as a Fresher. Well joke's on you, because not only there're people who only need at most 2 years to become a Fresher, by the time you graduated, they would already be a Junior/Senior and have at least tripled your salary.

Let that sink in for a second. You will graduate at 21. I'm 20 and I have the ability to build a software of a Junior Developer.

Conclusion

• Going to Software university in Vietnam is not a career start.
• Junior Backend is easier said than done.
• 4 years is the time it takes to become a Junior/Senior, not a Fresher.