I don't think there's much meaning in saying the Soviets outlawed capitalism.

Capital continued to exist and there continued to be people who decided what got built and who received them. To me, that's private ownership. I mean, it's not like apple trees suddenly began bearing Ladas. If I wanted to acquire a field to occupy / farm, it was presumably controlled by someone, either an individual person or group of people. I don't see the difference in saying that in one situation my neighbor owns the field as personal real estate, versus whatever terminology the soviets used for why I can't just take it.

> there continued to be people who decided what got built

The distinguishing feature of capitalism is that the people who decide what gets built are private individuals in competition with each other, and incentivised by profit to meet the demands of consumers.

In communism the people who decide what gets built are part of a single central authority with no competitors and no profit motive. That system doesn't work, which is why it collapsed.