I completely disagree with your last point. Social democracy has been wildly successful. Many socialist ideas work very well. The big problem with most "communist" countries is that they forgot the most important aspect: giving the workers a voice. They're supposed to be in the dictatorship of the proletariat phase towards communism, but none of them give power to the proletariat. They're a dictatorship of an elite, and there's nothing socialist about that.
And in the past century we've also seen the harmful influence of extreme capitalism on democracy, including social democracy. Clearly the power of money on politics needs to be limited.
But tue hardest problem is how to ensure that the voters are well informed. They need reliable news media, but the two obvious ways to finance that are through capitalism and the state, both of which are suspect.
Sure. You're talking about two different things here. When you're saying "social democracy", you're talking about "capitalism with a safety net". When you're talking about "Communist" countries, you're talking about a system in which the government controls the means of production. These are related but distinct ideas.
The thing is, in the "government controls the means of production", you necessarily cede to the government sufficient control of everything - news media and everything else: that is, by definition, totalitarianism. The government can easily use this to prevent "bad views" from being aired. It doesn't even require evil intent. The gov't can think it's doing the right thing by protecting people from "misinformation" - you can see this debate today in America, and I understand there's a debate today in Germany about actually banning an overly-right-wing political party. And when a government comes to view itself as being truly good, the only legitimate defender of the people, it'll be very tempting for them to stomp on media and even voting freedom even with those good intentions.
Socialism is not necessarily about the government controlling the means of production, though. It's about the proletariat, the workers, controlling the means of production. Government is one way to accomplish that, but that only works if the workers control the government, which was not the case in Soviet countries.
There are also other ways to have workers control the means of production to varying degrees. Labour unions, workers councils, etc share control between the workers and the owners. A democracy in which workers vote for a government that controls regulations is another. Co-ops are a great one.
And of course according to the communist ideal, there isn't even a central government to control the means of production.
The big questions are whether it's possible to reach that ideal, how, and whether it's even stable. Countries calling themselves "communist" in our world certainly failed dramatically. But social democracy has been fairly effective in giving at least some degree of control to the workers. Their big problem is that in a still fundamentally capitalist system, money still rules, and powerful corporations can often either control or ignore the government and take away the power of the workers. That has definitely happened in the US, and to a lesser extent in parts of Europe, over the past half century.
Social democracy is way more than "capitalism with a safety net". It normally advocates a mixed economy in which the means of production may still be owned privately, but the state may have various overriding powers such as:
And in the past century we've also seen the harmful influence of extreme capitalism on democracy, including social democracy. Clearly the power of money on politics needs to be limited.
But tue hardest problem is how to ensure that the voters are well informed. They need reliable news media, but the two obvious ways to finance that are through capitalism and the state, both of which are suspect.