Sure, and capitalism has never existed either, only specific forms of libertarian-constitutionalism 🤷♂️
Now, if you can see how silly what I just typed is, you should be able to see how silly it is to claim communism has never been tried. You say yourself that Marxist-Leninism is a communist ideology, so if it’s being attempted, then it’s valid to say a form of communism is being attempted.
Do you consider drastically improving upon previous conditions to be a miserable failure?
All of the citation needed. Don’t make the mistake of including the goals of outcome as part of the definition, that’s just cheating. Op obviously rejects the idea that it makes things better, you can’t just assume it a priori.