Click here to access article by Eva María from Jacobin.
This article is overly long and I think you can skip most of the first part. Why the author provides extensive quotes from capitalist media about the economic crises affecting these countries is a mystery to me.
To access some of answers to the question posed by the headline, I suggest that you skip down to the section entitled "Stuck in Capitalism". However, even here you will not find the unequivocal statement that socialism cannot be constructed in a state where the economy is primarily privately owned. The latter is what divides any society into two basic classes: capitalists and workers, and the latter typically divides into working class and middle class which is paid more and tends to identify with the ruling capitalist class (much like Malcolm X's description of "field niggers" and "house niggers". Native capitalists, especially when backed by the US-led Empire, will always find a way to scuttle such social democratic experiments.