Meanwhile the success in question: The 3rd world communist countries have managed to more or less industrialize and build up wealth, but under (state) capitalist system with all the bells of whistles which are markets, commodity production, wage labor, etc. In other words, they used capitalism to build up wealth.
Don't get me wrong, I actually think they had some absolutely amazing policies for the workers like free housing and social benefits, and good on them for building themselves up. However, this has nothing to do with socialism (socialist mode of production in this case) or communism as it was achieved with, and is therefore a win for capitalism - the same system that drove colonialism and the system that had already built up wealth for 'non-socialist' feudal/agrarian countries in the 19-20th century.
EDIT: Damn, judging from the amount of upvotes, it genuinely feels like walking into a bar and everyone drawing a gun and pointing at you. This is probably the most antagonistic I've been towards ML (or MLM/Dengist/Maoist) ideology and it's kinda disappointing how there's no actual non-ML Marxists to be seen here.