None of the current or previous countries are/ were Communist. A communist country is one that is stateless, classless, and moneyless. This hasn't appeared in any society aside from Catalonia, Spain, which was a success until the Fascists came and wiped them out in '39.
Socialism is an umbrella term that encompasses a lot of ideologies, but in common among these is a lack of government. Market socialism has cooperatives but is essentially Laissez-faire. Social democracy, what Bernie wants, is not Socialism, as it's pro Capitalism, just with integrated perks from socialism funded by taxes. The government doing more stuff is a contradiction to what left ideologies believe in. Now, setting aside those oppositions to the ideology via erroneous examples, here are a few other common arguments that I'll link videos to since it'll take too long for me to explain or because said creator is better at explaining.
Laziness - https://youtu.be/W61HHFv6WOM
Human Nature - https://youtu.be/P-MhzLMY93I https://youtu.be/EQnUFxoFqNY
Law Enforcement - (The video is in regards to Anarchism, but the creator is an anarcho-communist, so same deal. Just semantic differences.) https://youtu.be/Hmy1jjRnl8I
Also note that crime like theft, piracy, etc wouldn't exist within a communist society as there would be no need for it. Anyone who does commit some serious crime would instead be put into rehab rather than in jail, an institution communism is against as it's an exercise of state power used as a tool to oppress people (see incrimination ratios among ethnics vs whites and why the war on drugs was started)
For those concerned with drugs being an issue, look at Portugal and their plan in 2001. That'll show you making them illegal is bad. You also have to keep in mind that many turn to drugs to fill a void that Capitalism inherently creates, so there's be less abuse on top of Portugal's lowered usage rates from decriminalization.
Wage Labour is Voluntary - https://youtu.be/S_RcE2o08gA
For accurate I formation about the fall of the USSR that isn't "cuz communism" https://youtu.be/7khOpATj99I
For a quick video about Marx on Capitalism's potential consequences https://youtu.be/yynYFEp8H6w
And a I think behavioral psychologists quick 5 minute video that attaches the same sort of sentiment to our consumer based economy https://youtu.be/TIjvXtZRerY
On how Capitalism doesn't actually improve 3rd world countries https://youtu.be/JN6LlMY2ApQ https://youtu.be/4lDZaKjfs4E
For arguments against a pure democracy - https://youtu.be/pv_wAaohQ5k
It's, however, important to note that pure democracy does not have to insinuate mob rule. Those who work in the education sector won't have their votes or decisions influenced by those in the argiculture sector unless the population at large truly is dissatisfied with the handling of education and demand changes from the teachers. Within these worker owned sectors, each vote would be equal and horizontal while still being maintained by checks from the whole population, and these federations wouldn't exceed anything higher than 150 people, so no, power groups couldn't just up and give rise to some fascist regime and wipe everything out.
For elaboration on this (again this person is an anarcho-communist so it still fits)
Why we think capitalism sucks: https://youtu.be/gJW4-cOZt8A https://youtu.be/AR7ryg1w_IQ https://youtu.be/fCUTX1jurJ4 - while this video isn't strictly about capitalism, the problems it addresses are products of such https://youtu.be/BnbOGVDbPWc https://youtu.be/bnSiT_3sXDc https://youtu.be/w3AGe0ns_bw https://youtu.be/lMbvtmb79N0 https://youtu.be/AhRBsJYWR8Q Etc.
Why centrism doesn't exist: https://youtu.be/9e3_IKKb1fw
For those who think Marx was a statist - https://youtu.be/rRXvQuE9xO4
For those who think the left and Postmodernism are intertwined - https://youtu.be/cU1LhcEh8Ms https://youtu.be/26fIBA7O5Ag https://youtu.be/EHtvTGaPzF4
For those accusing us of cultural Marxism - https://youtu.be/qlrpSpwxgWw https://youtu.be/Ahuj1B0ow4U
On the presupposition that those in wealth could be for good (for those who acknowledge some of them are bad) https://youtu.be/ZSnXI93lY-0 https://youtu.be/5gnlhmaM-dM
For those who thinks we're all violent and violence is bad - you're stupid if you think were peaceful now, but https://youtu.be/vsRyTWBj84E And the existence of anarcho syndicalism and pacifism