It's for this reason that the creation of "socialism" understood as the abolition of private property requires the "all-round development of individuals". Only such individuals would have the developed "virtuosity" required to "appropriate" this form and these forces, i.e. "turn them into free manifestations of their lives."
“private property can be abolished only on condition of an all-round development of individuals, precisely because the existing form of intercourse and the existing productive forces are all-embracing and only individuals that are developing in an all-round fashion can appropriate them, i.e., can turn them into free manifestations of their lives.” <http://www.marxists.org/archive/marx/works/1845/german-ideology/ch03o.htm
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It's a problem for Marx's understanding of historical development that hardly anyone, let alone the "working classes", understands "socialism" in this way.
According to him, capitalism was to work to bring about both a felt "need" for and an actual significant degree of such "all-round development".
"What characterizes the division of labor inside modern society is that it engenders specialized functions, specialists, and with them craft-idiocy.
'We are struck with admiration,' says Lemontey, 'when we see among the Ancients the same person distinguishing himself to a high degree as philosopher, poet, orator, historian, priest, administrator, general of an army. Our souls are appalled at the sight of so vast a domain. Each one of us plants his hedge and shuts himself up in his enclosure. I do not know whether by this parcellation the field is enlarged, but I do know that man is belittled.'
"What characterizes the division of labor in the automatic workshop is that labor has there completely lost its specialized character. But the moment every special development stops, the need for universality, the tendency towards an integral development of the individual begins to be felt. The automatic workshop wipes out specialists and craft- idiocy." <http://www.marxists.org/archive/marx/works/1847/poverty-philosophy/ch02b.htm
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“the historic tendency of [capitalist] production is summed up thus: That it itself begets its own negation with the inexorability which governs the metamorphoses of nature; that it has itself created the elements of a new economic order, by giving the greatest impulse at once to the productive forces of social labour and to the integral development of every individual producer.” Letter from Marx to Editor of the Otyecestvenniye Zapisky 1877 <http://www.marxists.org/archive/marx/works/1877/11/russia.htm
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Ted