Originally, I was just another American kid who assumed that communism meant a brutal dictatorship with no personal freedom. After talking to a friend who was, at the time, more knowledgable about politics than I, I decided to do some of my own research on communism (reading Marx, reading about the history of states such as the USSR, etc.). What I ended up realizing is that the fundamental principle of Marxian communism is the idea that through workers controlling the means of production, society as a whole would benefit greatly. For this reason, I also believe that communism, when constructed correctly (which it hasn't been, but I'll get to that in a bit), is the purest form of democracy that we can achieve.
Basically, the way I see it is the basic principles of communism can lead to socioeconomic equality (which, surprise surprise, fixes quite a few other issues), which then paves the way for better standards of living for everyone and a true democracy. Obviously this is idealist and it wouldn't work perfectly, but frankly, capitalism isn't working very well at all and it never really has, so it's worth a shot, even if we're stepping into it relatively blindly.
As for historical communist states, I feel that the USSR had a lot of potential, and allowing Stalin to take power instead of Trotsky after Lenin's death was a huge mistake that led to the complete disaster (in a humanitarian sense) that we recognize as the Stalinist USSR today. Had Trotsky succeeded Lenin instead, I feel like we would see a very different story and many people would see communism in a different light. Trotsky was the "real deal" in that he advocated for socioeconomic equality, democracy, a permanent revolution, etc. while Stalin created his own pseudo-capitalist plutocracy.
As for the PRC, that one is a bit trickier, and to be honest I don't know nearly as much about it and I don't think that I should comment on that before researching it more. I will say that I'm not a fan of Mao though, as I feel that his adoption of Stalinist ideas and policies was terrible.