So Germany didn't have a penny to their name or any infrastructure to speak of after WWII, Belgium, France, Netherlands not much better. And even if you take Marshall Plan money into account, they were by no means wealthy countries when the Marshall Plan ended. But they have managed to increase the size of their economies by many multiples in the intervening 60 years....without being "pure capitalist" countries.
To put actual numbers to it, let's look at Finland. They went from a GDP of $53B in 1980 to $236B in 2016, per capita GDP from $11,000 to $43,000 (adjusted for inflation). And this huge expansion was during the time they had the most socialist policies in their history. (note the effect is even more dramatic for somewhere like Norway, I chose Finland because there's very little confounding impact from factors like natural resources). Again I think empirically there's little support for the fallacy that wealth only comes from "pure" capitalism and anything not pure capitalism drags an economy down, or that any socialist aspect of an economy are only being propped up by the "pure" capitalists. It is simply not reflected in the real economic data.
Turns out that free at the point of service healthcare, despite the fact that it costs money, can actually save the overall economy a significant amount because of productivity impacts. Turns out sick leave, even though it costs a company money with a naive view, might actually in aggregate save money from fewer contagious illness days and faster recovery times. Turns out keeping the elderly healthy and not requiring them to eat cat food might actually make them less of a drag on an economy, not more. And that's before you put a value on the overall happiness of your population that doesn't have to worry about getting wiped out by medical bills, a stint without a job, or simply old age; GDP isn't everything. It's an Ayn Randian fallacy that only "pure" capitalism creates value.