You or I could theorize about the causality, but I would say it’s very hard to deny that there’s a correlation.

You've yet to point out any correlation. I specifically pointed out how there is no correlation. Which you just ignored or hand waved away completely.

The Sinovac vaccine was very different from the Moderna vaccine

Yes but it's hard to know where to start with the problems with this statement. First that's not a creation of the Soviet Union since it hasn't existed since the early 90's. Further the efficacy of a vaccine is non sequitur. You said it was capitalism that gave us vaccines. Yet non capitalistic systems make them too. So you move goalposts claiming they aren't as effective. If you're going to make an argument stick to it.

Soviet computing and heavy industry was far behind the West for the whole of the USSR

Again not relevant. They shouldn't have had any at all if it was capitalism that gave them to us. The fact they were making their own in any capacity disproves your statement.

We didn’t have millions of people dying of starvation, for one.

At that exact moment? Maybe not. We've had our own famines however. And starved an uncounted number of people. Even then, those famines were not caused because communism. They had nothing to do with communism. They were naturally occurring famines. Made worse by unanswerable ignorant authoritarian leaders. Unwilling to listen to actual experts or those with experience. It had nothing to do with any actual social or economic policy inherant to socialism/comunism. But if you disagree please point out where in Marx's writing the fault lies. Engles is a spiteful lunatic who's musings and philosophy have caused untold damage to the ideology as a whole. But even his philosophy didn't cause the famines. But if you disagree please explain how "because communism".

If you’re saying USSR and China don’t count, what does count?

I'm not saying that. They do. Naming something Communism or Communist doesn't make it that. There are specific points that make something communism. Which none of those countries really have had. Specifically they're Marxist-Leninist. Though Lenin's ideology runs counter to a lot of Marx's. Making that label an oxymoron more than anything. Regardless, marxist-leninism wasn't and still isn't communism. It's goal was to develop the infrastructure to the point that somehow. Through hand wavy magic the powerful autocrats in charge would magically give up their power and control, switching everything to communism when the time was right. Yes, it's stupid magical, and irrational thinking. But not communism

Where has what you think would work better in the US been done on a big scale, and worked well? That’s not some kind of rhetorical question, I really want to hear what the answer is.

Most the rest of the industrialized world. No really. Most have single payer. It works well. Scandanavian taxation, regulation, and governing philosophy. It's not perfect, but far better than what we have in the US. Not to mention their public central heating. Austrian style public housing. It's comfortable, affordable, and many of their celebrities even choose to live in it even. Public high speed rail and mass transit like Europe and much of the rest of the industrialized world. The sort of stuff capitalists and capitalism keep us from. Not because they don't work. But because there's no money in it for them.