The problem with Communism is that the few who gain power will alter the rules of the playing field. People are greedy in general and that's the rule we need to assume. Look at Mainland China in the past and even today. Mao became a mad king and set China backwards several decades. He killed any and all wealthy people, even though, logically, not all rich people are bad people. By killing off the wealthy (people who were well educated), he was left with farmers and other low level workers. Not to mention, he tried to destroy 5000 years of Chinese culture. After Mao's death, the Party did change course, but to this day, China isn't the kind of place people can truly find happiness in. Today, they have a Capitalist economy mixed with Socialism and Dictatorship. People do not own property as they all have an expiration date of 70 years. People do not have human rights; if they speak up or protest, they get thrown in jail. The air quality is the worst in the whole world. Wealth gap between rich and poor is so bad it even surpassed the United States. When you have connections with Government officials, you have a much higher chance to become wealthy. There is no public funded healthcare. Many people have become selfish, throw trash on the ground, pick fights with you, spit in public, etc. It's funny that a so called Communist country has the most people who worship money.
Contrast all that to a different country, The Republic of China (Taiwan). When the Nationalists fled to the island of Taiwan after losing the Chinese Civil War to the Communists, they moved the Republic of China Government from Mainland China over to Taiwan. While Taiwan was ruled under decades of Dictatorship, the ROC constitution was one that set eyes on Democracy. The founding father of the ROC, Sun Yat-Sen, fought for Democracy since 1911. Taiwan today is a successful, stable Democracy, with full human rights protected under their constitution. Their wealth gap is one of the lowest if not the lowest in all of Asia. Freedom House even ranked Taiwan more free than the United States this year. They maintained more of the 5000 year Chinese culture than Mainland China does to this day. They have a successful single-payer healthcare system since 1995. They have affordable housing overall with average wages twice as high compared to Mainland China. Their people are well mannered, cheerful and helpful. They take their recycling very seriously and their air quality is much better. In a lot of areas, Taiwan functions like a Social Democracy or Democratic Socialism.
I am a Social Democrat as I believe people need to be given the right to own property, but there needs to be strong social programs that benefit society as a whole. From the examples above, it is clear why I believe what I believe.