Communism always fails and always will fail based on the fact that it absolutely requires a centralized force to maintain it (as does capitalism, but hey at least we can admit it), which invariably becomes corrupt in their new system and the de facto neo-"bourgeoisie", with all the negatives of capitalism. Add the fact that all internal competition is removed (can't have those pesky markets) and you get a world not dominated by Google and Facebook, but rather a government that runs a shittier version of Yahoo Geocities. But hey, at least it's owned by "The People" (e.g. the totally non corrupt or stagnating government)

They can create some lovely abstract pictures of a perfect society to fool the pseudo intelectual into thinking there can be such a thing as a "classless, stateless, etc.less" society, coupled with innovation, post scarcity and ascendant scientific prowess... all bullshit, all to create acceptance of means to an end, an end that never happens.

First of all, anarchy (the supposed end goal of communism, statelessness) can't exist... its inherently unstable, a vacuum. The answer why is pretty obvious, opportunists abound... even a small ready military force could crush any unprepared "people's defence force", especially with modern weapons that force multiply by many orders of magnitude. There's a reason all major states have standing armies today. Standing armies pretty much necessitate a government, which (by definition) necessitates a ruling class.

As for some of their advancements, the Soviets won the war and got to take half of the much more advanced European continent, then pulled the same thing the US did by pulling in highly skilled scientists and growing into the vacuum left behind by the shattered European empires. They did build a decent STEM education system, but they were never able to really apply their national brain trust to anything but government sponsored programs designed to lord over the Americans; hence why the majority of their populace shared bathrooms and lived in shitty block housing. Both they and the Chinese had major advancements, but that has more to do with with how ass-backwards they were before and less with how great communism worked out for them. I'm willing to bet North Korea could open up to the outside world under communism or capitalism and have massive advances either way.