I have to disagree with your argument, namely the “as it is practiced” part of your thesis, which implies a better, “more Christian” version of capitalism is possible.
I haven’t been a Christian since I was a teenager, but since this is a debate about whether or not capitalism is Christian, I’ll frame this in theological terms.
For starters, your description of communal living in the early Christian Church is incorrect:
Christians were still in possession as private owners of homes and still met as congregations in private homes.
You quote Acts 2:25, but Acts 4:34–35 says:
There was not a needy person among them, for as many as were owners of lands or houses sold them and brought the proceeds of what was sold and it was distributed to each as any had need.
In other words, they abolished private property and lived in accordance with the maxim “From each according to their ability, to each according to their need.” That is communism in its purest form.
You then emphasize that this was a free choice. Sure, but so what? That has no bearing on whether or not their actions were in accordance with God’s will. The early Christian church was the purest expression of Christian principles, and I don’t really think the scriptures could be any clearer about what that entailed. They chose to follow God’s will, but it was God’s will nonetheless.
I’d also like to direct you to the words of James the Just, brother of Jesus, the man who better represented the spirit of Christ’s teachings than Paul.
Come now, you who are rich, weep and wail for the misery to come upon you. 2Your riches have rotted and moths have eaten your clothes. 3Your gold and silver are corroded. Their corrosion will testify against you and consume your flesh like fire. You have hoarded treasure in the last days. 4Look, the wages you withheld from the workmen who mowed your fields are crying out against you. The cries of the harvesters have reached the ears of the Lord of Hosts.
This is a fairly straightforward condemnation of exploitation and obscene wealth, which are both inherent in capitalism. You can implement laws to mitigate some of the excesses of capitalism to a certain extent. You can also create a robust welfare state, but the nature of capitalism is exploitation of labor, which is to say paying workers less than the value their labor produces.
Neither James nor Jesus had an understanding of political economy, so of course they framed it as a moral issue, but they had an intuitive understanding of what justice looks like.
But back to property—there is a simple theological argument for why private property isn’t Christian. God gave Adam and his descendants (i.e. everyone) dominion over the whole earth. The riches of the earth—the land and all other resources—are our inheritance to collectively have and possess.
The Original Sin of capitalism is the original appropriation of this natural inheritance for private use, and all the other sins capitalism are in one way or another derivative of this theft from the commons.
Even if a person starts with nothing and saves up their whole life to buy property honestly, it is not theirs to buy or the sellers to sell. This is not to mention the whole host of other sins that were involved in the creation of American capitalism: the genocide of native peoples, the theft of black bodies and labor.
There is nothing one can do to humanize or Christianize capitalism.