Imagine the sentiment if the question was 'Fascism has never been truly tried'

I would argue that many forms of "communism" have been tried at many different scales. Thus far, it only can retain stability in small, intimate groups where everyone knows everyone else. Marx himself was partially inspired by hunter-gatherers, who have basically no personal property and insist on little-to-no hierarchy and sharing of resources. Truly "To each according to need. From each according to ability." This was stable for 95%+ of our time on the planet. Once the groups get too big, you start to fracture. People in your "group" are who you are socially accountable to. All the others are essentially "statistics". People will always prioritize their group over other groups. So hierarchy and power-mongering are essentially inevitable. Especially since they usually come into power as a single-party government.

Communism has not only been tried but has proven a success in many places it was tried. There were some bumps in the road, a lot of mistakes made, but we can't ignore the fact that Russia under Lenin and Stalin industrialized and modernized within a few decades from a backwater feudal agrarian society to a modern industrial power. China has lifted nearly a billion people out of poverty and has modernized as well. Cuba continues to have the best healthcare system and the best education system in the western hemisphere despite the embargo by the US. Vietnam has the fastest growing economy in the world. The DPRK still persists despite the efforts by the west to destroy it. People in former Eastern Bloc countries overwhelmingly miss living under communism. While "shock therapy" liberalism destroyed most of Eastern Europe, Belarus averted this fate by keeping its Soviet-style planned economy. Russia is bringing some elements of that back, under Putin it has become a Nordic Model style social democracy. In fact, I can think of only two instances where communism failed, and it was because of the foolish men implementing it, Ne Win's Myanmar under the "Burmese Way To Socialism" was a disaster because he used superstition to guide national policy and he had no idea how to run an economy and Pol Pot's "Democratic Kampuchea". Luckily, Vietnam removed Pol Pot from power and established a more successful, sane version of communism.

I think for this situation: It depends what you mean by communism. If we're talking about any type of planned economic system with some sort paramount government dictating markets and little to no private property, well yes that was tried many times (Russia, China, Vietnam, etc.) But if we're talking about establishing a political and economic system that accurately followed the sequence of the Marxist Dialectic under the Orthodox Marxist premise of a bottom-up international revolution, well that has never actually happened. To be fair, Marx was a great critique with an enormous impact on modern social science, but his solution to capitalism weren't always grounded, forcing future socialist states to depart from Marx's original vision. Both China and the Soviet Union's rise to power came with changes in their Marxist doctrine, creating their own version. Leninism established the Vanguard party which safe guarded the revolutionary agenda and were basically gatekeepers to keep the proletariat in check and prevent any sort of dissonance within the party. Leninism also introduced nationalism to the revolutionary mix despite Marxism's scope on an international revolution. So yeah Communism has been tried but many variations are still untested. It ain't easy establishing a theoretical political system when Capitalism encompasses most of our daily experience.