The idea that China was socialist under Mao but became capitalist under Deng is a common Maoist take and something that distinguishes them from Marxist-Leninists, it's kind of in the name.

Sometimes when people call China capitalist, I half-jokingly ask if they're a Maoist, or if they think the best policy is closer to Mao than what they're currently doing. Of course, usually, the answer (when I get an answer at all) is no: they opposed what China was doing when it was more state-controlled and they opposed what China was doing when it did reforms and opened up to private investment, if they make moves to hold billionaires accountable to the law or to move more of the economy to the public sector, they're bad, and if they did the opposite, that would also be bad, but if they stayed steady, that too would be bad.

Maoists and Capitalists are both at least coherent in what they think China should do, in opposite extremes: either undo the reforms and revert to how it was or liberalize further into a fully capitalist state. Marxist-Leninists tend to have more nuanced takes about adapting to changing conditions, in line with what they've done. But then you have this other category that's super prevalent on Lemmy that wants to criticize China's every move without ever offering any kind of coherent idea of what they actually want them to do, economically. I don't even know what to call that position because it's utterly incoherent.