Communism comes from capitalism. Capitalist transforms small-scale industry centered around private production and private appropriation into very large scale socialized production, while still maintaining the structure of private appropriation.

This leads to contradictions in the economic system as you have well-organized enterprises with sometimes millions of workers working together collectively to produce all the wealth, but then the wealth is privately appropriated by a small handful of people.

Naturally, this growing contradiction gave rise to people who believed in transforming private appropriate to socialized (i.e. collectivized) appropriation to resolve the contradiction with socialized production.

Capitalism's development gave rise to Marx and Engels, and it is successful. China is the leading economic power on earth, and the overwhelming majority of large-scale enterprises are nationalized. A significant portion of the GDP output is directly from the public sector, and the percentage that is not is basically equal to the percentage of the GDP output produced by small-to-medium sized enterprises (SOEs).

The nationalization of SOEs never made sense from a Marxian analysis and was opposed by many Marxists prior to the USSR such as Marx, Engels, Lenin, Hilferding, Bukharin, etc. The Stalin Model was kind of Stalin's own thing, and it worked great as a way to rapidly transform a feudal country to an industrialized nation, but struggled to make that industrial growth sustainable.

For some reason, the leftcoms and the liberals have joined forces in claiming that "true socialism" is only what the USSR did, even though it blatantly contradicts Marxism and was more just something unique to the Soviet conditions at the time, and they say that any country that actually follows a Marxist development model like China is "not true socialism."