The answer to the question in the OP inherently gets you into "what is socialism" territory.
In theory:
First thing to point out is how capitalism avoids the question of scarcity. If you've got an item where supply is scarce under capitalism, then theoretically you can just keep upping the price until only a minority can afford it, at which point the shortage at issue appears to be consumers' money rather than the product.
If however your society takes it upon themselves to provide every member of society with particular products or tries to establish set maximum prices for that product that everyone can afford on a government-set salary (as state socialist societies tend to do), then whenever you experience a limit in supply then you produce a shortage.
Imagine Britain decided tomorrow that it was everyone's birthright to eat Kobe beef and decided it would be provided free of charge on the National Food Service. Without having done anything to production, you've instantly produced rationing, queues and shortages. The shortage could be alleviated instantaneously by reintroducing a free market in kobe beef, and allowing scarcity to be "solved" by market prices. People are still going without kobe beef, but now the scarcity is organised by wealth, not universal. All without doing anything to production.
In practice:
To massively over-generalise, productivity and resource distribution in many industries in state socialist countries has often been historically inefficient because when basic subsistence is provided as of right by the state, management lack sufficient means to discipline or motivate their workforce. Sometimes they correct this by turning to violence or offering incentives.
In Venezuela:
Much of the country's capital is still owned and run by private capitalists who are reluctant to produce goods which are unprofitable because of government price regulations.
