It seems like we disagree about what it means to actually propose policy.
> Capital is pretty pure critique of the then-status-quo
Yep.
> The Communist Manifesto has a fairly broad program
The Communist Manifesto doesn't do much policy proposing. Workers owning the means of production is about as far as it goes, and to the extent that that his Marx's proposal...that isn't realized anywhere in Europe.
> but narrower and less-well-known works like the Demands of the Communist Party in Germany
https://www.marxists.org/archive/marx/works/1848/03/24.htm
https://www.marxists.org/archive/marx/works/1880/05/parti-ou...
These are both pretty short and vague, but they are policy proposals. However, they are both pretty clearly not an articulation of his vision for the post-revolution society he describes in The Communist Manifesto. They are pragmatic demands for political parties to make of their governments.
Let's compare. The Communist Manifesto:
> In this sense, the theory of the Communists may be summed up in the single sentence: Abolition of private property.
Demands of the communist party in Germany:
> 15. Introduction of strongly progressive taxes and abolition of taxes on consumption.
So, here's the fundamental issue: When Marx is specific, he's mild. His specific ideas are totally bland, and not at all unique to him. He would be a footnote of history if his specific ideas were all he said. When we refer to "Marxism", we refer to the actually novel idea: Abolition of private property. But of course, it is here that he is vague. He gives no indication of how a society without private property might actually function. And it is into exactly that void that Leninism stepped. It did so because it had no choice.
Lenin understood that they didn't have a revolution to institute a minimum wage. They had a revolution to abolish private property. But Marx had no clue how to manage such a society, and as it turns out, neither did Lenin.