The CPC did not “swing back to the previous party line,” they continued to change tactics as material conditions changed, while holding to the same overarching strategy. Xi Jinping built on what was achieved before him, he did not simply “course correct.” As Reform and Opening up facilitated more stable and slightly accelerated growth, there arose new contradictions. The Xi Jinping era took the newly developed productive forces to help address these issues, without the benefits of Reform and Opening Up this would have been more difficult and protracted.

I am not as familiar with the CPV, but wanted to comment on this bit as it’s crucial to understanding not only China, but any country building socialism. There is no “socialist formula,” we have to adapt to our existing conditions.

Vietnam is basically following China’s playbook but just 10 years behind. Like China, they allowed foreign capital to come in order to build their industry. Once they have good manufacturing, they will increase socialist aspects again.

Luna Oi! is a great source, comrade. See her (YouTube) video about Vietnamese textbooks, for example. The ending hints at the answer you’re looking for.