Yup, socialism and communism only works on the start, but there are a few good effects of communism and socialism, they've improved living conditions of the poor people, but only this... Moatly it just kn the long condition doesn't workEh. It works great in the short run. But when resources, and more importantly, money, runs out, the systems collapse in on itself, as have been shown constantly throughout history. Neither system is viable in the long run as far as the economy is concerned. You have no source to bring in the money from as people are not motivated to get a high-paying job. Because why bother getting a triple-digit+ salary when you will simply get your shit taxed to death anyway to support people who may not even deserve it.
The USSR is dead. Venezuela's currency, Bolivar, is worth less than World of Warcraft gold and its social infrastructures are imploding. Venezuela is a country that supposedly have large oil reserves they could use to boost the economy and create a proper infrastructure, but their oil is worthless.
Communism and Socialism are systems, socially and economically, that just can't survive on their own. They need Capitalism in order to survive, or they will slowly choke themselves to death. And when you implement a different economical system it's in essence not Socialism or Communism, but a mix.