If economic systems are morally ambiguous, then why does each have serious ethical implications?
In the case of communism, the lack of private property means that workers are virtually unable to earn their true value. Since the means of production are controlled centrally, private citizens have no means of entrepreneurship. They are completely reliant on the government, which in many cases, such as the USSR, does not have their best interests in mind.
The same goes for capitalism, which perpetuates inequality within society. While some are incredibly wealthy, more suffer from crippling poverty. With millions of struggling families, it's difficult to paint capitalism without moral implications.
Lastly, socialism suffers from the same issues as capitalism and communism. Each system has moral failings, and can't be separated from them. Economic systems are central to society, and to paint them as systems without moral implications is inhumane.