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 take it further and become more capitalist. 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 makes no sense to me at all.

Maoists are ultraleftists, they generally deviate from Marxism to an idealist, rather than a materialist degree. I recommend checking out my comment responding to them.

The Vanguard concept isn't flawed, it has real basis in materialist understanding. The idea that AES states have "devolved into Capitalism" is wrong as well (except the USSR into the various post-Socialist states). I recommend reading both Why do Marxists Fail to Bring the "Worker's Paradise?" as well as Socialism Developed China, Not Capitalism. The Dengist reforms were a reversion back towards Marxism, Mao had tried to achieve Communism through fiat without enough development of the productive forces and as such there were struggles and recessions.

Public Ownership and Central Planning works best on monopolist syndicates aquired by the State, that's the entire reason why Marxists say Capitalism creates Socialism and that the bourgeoisie produces its own gravediggers first and foremost, this monopolization into internally planned syndicates makes Socialism a natural evolution on Capitalism, not a "better society" to force into existence.