I don't have the mental power at this moment to write out my full thoughts on the subject so forgive my vague thoughts (an aside- withdrawing from SSRIs is an _unpleasant experience_)
I think the problem I find with arguments that Capitalism is the best/least bad system tend to be that they start from a false premise, in my opinion. I have a friend who makes the joke all the time that any system of government works if people were just nice to each other, but he has a point. I often hear that "oh, communism doesn't work because humans are inherently selfish." That's true, if you believe that humans are inherently selfish, but my counter-point to that is asking how much of it is innate vs. how much of it is trained by our culture and reflects back in those communist attempts because the sudden change in social architecture didn't give enough time to 'train it out of' the culture.
Back to the thing my friend says - if you believe that communism doesn't work because humans are inherently selfish/greedy/etc, I'd say to you also that capitalism is currently not working _because humans are being selfish and greedy_ in a system _that explicitly rewards that_. Which, maybe is worse.
I don't pretend I have an answer for how we can get from point A (capitalist system) to point B (future space communism) in a way that slowly shifts human thinking towards mutual aid and collective action, but I think it's short-sighted to assume that the way humans act in a system that rewards greed/selfishness is innate.
But, to your other point, I think human greed is innate. I can't think of evidence that would suggest that greed is somehow cultural or learned. Boil the system down to the lowest common denominator, you find greed. Scale it up: greed. No matter what you do, you cannot remove human greed systematically.
For example, do you believe the Capitalist system has nothing to do with the eagerness of the United States to drop bombs throughout the world for the past 100 years? Personally I see these actions as unnecessary and evil but pushed to continue by the people who stand to gain the most wealth and influence from them.
Musk and Trump are doing a Holodomor in front of the world's eyes.
I ask because if we can take a country with a communist economy, or striving for one, and blame all its evils on communism itself, I have a few things I'd like to point out as being the horrors of capitalism:
1. Atlantic slave trade - millions dead (many on the ships), millions enslaved
2. Settler colonialism and indigenous genocide - British empire, all over the world
3. Congo Free State, Leopold II - 1 to 5 million dead via colonial extraction regime
4. British India famines - 3 million dead
5. Irish Famine - 1 million dead
6. Opium wars - directly caused by British using the military to defend market access. 100k dead, devastating to Qing China for a century
7. Indonesian anti-communist massacres - 500k-1mil alleged "communists" killed after the USA, UK, and Australian intelligence agencies propagandized against them
And I attribute them to communism because that's literally how history attributes them, though obviously pro-Communism thinkers would disagree.
The 1956 student massacres in Hungary, where my grandma was almost killed. The Holodomor, the various "Russianization" campaigns, the Jewish Autonomous Oblast, The Great Leap Forward, etc.
B) Fine, drop communism altogether -- it's evil and disgusting and bit my finger and should never be tried again. Can we work on a society where the means of production are owned by groups of laborers?
I have good news for you. As someone in my job's ESPP plan and with a 401k, it already is!