...and contradiction in proletarian practice
If Marx was perhaps the writer who went the furthest in extolling and rejecting democracy, it's because he expressed in its most concentrated form the forced situation in which the proletariat used to live and still lives. Intellectual discrepancies mirror a practical dilemma which the proletarians have to solve to emancipate themselves.
Like others in his time, like R. Luxemburg later, like the German Left after 1914-18, Marx reflected a contradiction: self-awareness and "community culture" (Selbstverständigung and Versammlungskultur, as they were called in Germany around 1900), both in the workplace and in the workers' district, confront bourgeois democracy with proletarian community. But using one's condition as a major weapon is a double-edged sword for the proletarians. Guy Debord may not be the most acute critic of democracy, but he points to something essential in The Society of the Spectacle, theses 87 & 88:
The bourgeoisie was able to use its socio-economic power as the main instrument of its political ascent. The proletarians can't use their social role to emancipate themselves, because this role is given to them by capital. So their only radical weapon is their negative potential... closely linked to the positive part they play in the reproduction of capital. The bourgeois won by asserting themselves on the basis of what they already were socially speaking. The proletarians can only win by fighting against themselves, i.e. against what they are forced to do and be as producers (and as consumers...). There's no way out of this contradiction. Or rather, the only way out is communist revolution.
It was enough for the bourgeois to get together and find the means to run society: so creating suitable decision-making institutions was enough (though it took centuries). It was not only for the sake of culture and enlightenment that from the 18th century onward the ascending elites promoted networks of debating and scientific societies, clubs, public libraries and museums, and of course a growing press : the rising merchant and industrial classes were building up a new type of sociability that helped them challenge monarchs and aristocrats. The proletarians also need to get together : but for them, merely getting together is staying within capitalism.
For what it is worth, democratic reunion is enough for the bourgeoisie. The proletariat needs something else. Proletarian self-organization which fails to develop into a self-critique of wage-labour reinforces labour as the partner of the capital-labour couple: the forced coupling goes on and so does the management of the couple, hence the peaceful coexistence of opposites called democracy.
The partial, confused, yet deep communist movement that developed in the first half of the 19th century initiated an equally confused yet persistent critique of democracy. Both movement and critique were soon pushed to the background by the rise of organized labour that tried to make the most of bourgeois democracy. Yet every time the movement re-emerged, it got back to basics, and revived some aspects of the critique of democracy.
There's no need to be an expert in Marxology to know that most of these fundamentals fell into oblivion: some texts got hardly any response, while others were put aside by Marx and Engels and published much later. The "real movement", as Marx called it, seemed to have very little use for these writings. In the first half of the 20th century, new proletarian shock waves led to a reborn critique that (re)discovered these long-forgotten intuitions, but failed to be up to them. Indeed, Bolshevik practice after October 1917 could fall within Marx's critique of the French revolution and of Jacobinism. As for the worldwide 1960-80 earthquake, it turned out to be a zenith of democracy as it over-emphasized anti-bureaucratism. The theoretical paths signposted over 150 years ago have yet to be followed.