To answer your question first, but with another question, are there still socialist on this planet?
No, socialism is not beaten by capitalism in every round. A closed capitalist system that does not have the education and resources can fail, even faster than a socialist society will ultimately fail. Such societies usually do not climb above minimum, hand to mouth levels either. Without an infuse of capital and knowledge, they simply cannot climb higher or will take centuries to do so while other societies advance even further ahead. To date, Japan, is probably the only society that ever could be called successful while using a closed capitalist system. But then, it did receive a lot of help following WWII, so it did not truly start as a "closed" system.
Socialism is not always a failure at the start. Like a hydrogen fuel cell, it will take awhile to totally run down. It will however eventually run down because it always ends with the system attempting to equalize output for all without equalizing the input of all. It is impossible to get more out than what is put in. At it's core, Socialism seeks to create a "classless" society, in order for society to be without "classes" everyone must ignore value and also, everyone must be made equal regardless of their individual input. It is impossible to equalize every one at a high level because it draws more off of the system than is put into the system. Unfortunately for those who adhere to such a philosophy, there is no way to make all people truly equal. Each person has a unique combination of talents, intelligence, drive and education. It also does not encourage higher output from individuals, it cannot without creating class. In the end, the only way to equalize a society and do away with "class" is to have everyone at the lowest sustainable class level. For human societies, that is the slave class. While the individuals in such a society would not have an individual "master", they will be slaves to the society as a whole, but slavery is still slavery whether serving an individual master or a societal/community master. For those who do not believe it is true slavery, then perhaps you should check out what Marx says should be done to those who "revolt" against socialism.