I see Chinese citizens traveling abroad every day. Doesn't look like they cannot travel. Freedom of what exactly? Are you really free in America when you have to toil away 12 hours per day to make ends meet? Honestly funny to see people falling for American propaganda.
They only let some of them out. And it's hard to get a passport. Most other countries work the opposite way. You need approval to enter. In China, you need approval to exit.
One way to think about it: if every country prevents people from entering, the effect is exactly the same as one country preventing people from leaving.