I do think higher-stage communism in one country is questionable, but this was a very late opinion of Stalin and not something from any of his earlier works, so it’s not really relevant to what most people mean by Marxism-Leninism, which is centered upon what he wrote in Foundations of Leninism. Marxism-Leninism is not some pro-Stalin cult (which may be surprising to hear if a Trotskyist is reading this, as they are a pro-Trotsky cult), so it doesn’t imply a belief in everything Stalin ever wrote. I’m sure if you asked the majority of Marxist-Leninists if the higher-stage of communism is possible in one country, they’d say no.

We can cherry-pick Stalin all we want to find things that people may disagree on, but that doesn’t establish that there are groups of people who going “parroting things that clash with Marx believed in” unless you can also demonstrate that this opinion is something widely held. I’ve never seen evidence of it being so. Marxism is also not a religion anyways, we shouldn’t be focused on strict adherence to “what Marx believed in.” Marx’s intention was to create a scientific method of analysis for socioeconomic development. Even in cases where you can find a group of Marxists who clearly disagree with something Marx held, that in and of itself doesn’t matter; what matters is the reasons they disagree with it, and whether or not their new analysis makes sense.