Why does the added qualifier in your first paragraph matter?

You’re literally just explaining why the Soviet Union was less successful.

Nothing stopped the Soviet Union from liberalizing their economy and running it better like China. They just didn’t do it. Which loops us back to my original comment.

I didn’t bring my point up as some kind of communism versus capitalism thing, I’m just plainly stating that as far as single-party mostly-authoritarian governments go, China is far more accomplished than the USSR was.