That's a major point of the article. In his work you have a part in which he identifies the problems (eg Das Kapital) and another part which proposes a solution (eg The Communist Manifesto). In medical terms Marx made a good diagnosis, but a bad prognosis (as demonstrated by history).

I think it's important to differentiate them. Marx wasn't a religious prophet, you can take the good stuff and leave out the bad. Even he said in his later life that his goals could be achieved by democratic means.