Words have different meanings in different contexts. Yes, China isn't the perfect theoretical communist utopia predicted by Marx. But in the English language, people call the type of government system used by Stalin and Mao "Communist." A word was needed for their systems, as it was clearly different from capitalist countries. And Stalin and Mao themselves called their systems Communist. And their systems aspired to the vision of Marx. They both considered themselves to be Communist and fully identified with the term. So we call that system Communist. Whether it actually lives up to the theoretical model of Communism is irrelevant. When people use the word "Communist," they are referring to the type of government created by Stalin, Mao, etc. This is theoretical vs applied communism. You want to only apply to the word to theoretical communism. But the English language uses it to apply to both theoretical and applied communism.

Capitalism looks very little like the theoretical models crafted by people like Adam Smith, yet we still call Western governments capitalist. Often the theoretical proves impossible to implement, so the label gets applied to the practical implementation, not the theoretical ideal.

When you say, "but China isn't Communist!" you're not actually accomplishing anything. You're just arguing that a definition that has been commonly and widely used for over a century at this point is invalid. People have been using "Communism" to refer to both applied and theoretical Communism since at least the 1920s. I know you want to only use the word to apply to theoretical Communism, but the whole world moved on from your viewpoint a long time ago.