It ultimately depends on how broadly we define socialism, but we could either describe China as a far from perfect socialist project that is currently still in the state capitalist stage of development in the Leninist sense or even a unique form of early-stage market socialism carefully building towards a later higher stage of socialism (this of course assumes that you subscribe to the idea that socialism can coexist with commodity production and the law of value which left-coms who reject even the USSR as state capitalist also would definitely reject).

China's economic model is very similar to what the Soviet Union was under the NEP (New Economic Policy) that Lenin championed as a necessary strategic retreat from the previous economic strategy of War Communism (which had practically everything nationalized and centrally planned). Lenin argued that the NEP and state capitalism were required to attract foreign investment and build the productive forces necessary for socialist development. According to Lenin:

For socialism is merely the next step forward from state-capitalist monopoly. Or, in other words, socialism is merely state-capitalist monopoly which is made to serve the interests of the whole people and has to that extent ceased to be capitalist monopoly.

Under this economic model of the NEP, the commanding heights of the economy (heavy industry, natural resources, and banking) remained under public ownership with a large private sector allowed to exist outside of those strategic industries along with the establishment of a new small class of capitalists called "NEPmen" that were excluded from any real political power. The NEP was eventually ended by the Soviet leadership under Stalin as he argued that state capitalism under the NEP despite its achievements in helping to rebuild the Soviet economy after the civil war would still not allow for the rapid industrialization that was believed necessary at the time to defend the USSR against Western imperialist aggression.

Deng argued that China had become economically isolated in a capitalist-dominated world (the Sino-Soviet Split exacerbated this situation) and was still deeply scarred with the poverty and economic backwardness from China's era of semi-feudalism and consequently lacked the productive forces, technology, and know-how to immediately jump into becoming a successful fully centrally planned economy of 100% social ownership like many in Mao's faction of the CPC wanted.

So, Deng Xiaoping advocated for an transitory economic model of a "socialist market economy" that he developed from studying the Soviet NEP that would still place China within what Chinese communists had called the "primary stage of socialism" where certain aspects like markets and limited forms of private ownership outside of major strategic sectors of the economy that comprise the commanding heights of the means of production would be allowed like private ownership of less important light industry and consumer goods/services under Communist Party supervision with a strong emphasis on joint ventures with foreign Western companies that would require critical technology transfers from foreign capitalists to the Chinese public if they wanted access to the Chinese market:

By carrying out the open policy, learning foreign technologies and utilizing foreign capital, we mean to promote socialist construction, not to deviate from the socialist road. We intend to develop the productive forces, expand socialist public ownership and raise the people’s income.

However, by allowing foreign capitalist companies to employ Chinese labor, this does of course come with the negative consequences of more exploitation of certain workers during the "primary stage of socialism" but is still seen by enough of the CPC as a necessary evil for a middle income developing country to acquire foreign capital and technology that they contend are necessary to avoid becoming economically isolated by capitalist encirclement while also building productive forces. Made in China 2025 is the current government initiative that has utilized past technology transfers and Chinese industrial policies in a campaign to position China as a global powerhouse in high-tech industry. Nevertheless, the reform and opening up era still had a lot of harmful excesses from the market reforms in hindsight like the partial privatization of healthcare that the current government under Xi is trying to fix with the Healthy China 2020 and the Healthy China 2030 initiatives (Universal healthcare is claimed to have been just recently achieved by the government, but still is not free at point of use despite better coverage and affordability). The staff and workers' representative congresses also lost power during the 90s under Zemin, but have been re-strengthened under both Hu Jintao and more recently under Xi. There was also an explosion of corruption and inequality due to the market reforms that the CPC didn't handle or prepare for particularly well until more recently with the anti-corruption campaign of Xi's administration and the recently revised tax code that lowered the tax burden on the working class while increasing taxes on the wealthy and enforcing taxes on global income that disproportionately affects wealthy Chinese. Excessive inequality will undermine China's dual circulation strategy.

The "socialist market economy" that the CPC established retained public ownership over the commanding heights of the economy (the state has an effective monopoly over banking, finance, heavy industry, energy, mining, transportation, metals, telecommunications, natural resources, land, and public utilities) while also having many local or provincial state-owned enterprises in many other industries including the auto industry, pharmaceuticals, and IT as well as many cooperatives especially in agriculture. Central state-owned enterprises were consolidated to be much fewer in number but also significantly larger in size and total assets while also becoming more efficient, comprising nearly 2/3 of the top 500 companies in China. The Chinese government also has varying degrees of minority ownership in many private enterprises in China. The size of the Chinese private sector can be inflated at times by having cooperatives and mixed enterprises of mostly government ownership with little private ownership be included as part of the private sector.

Just as the Soviet NEPmen were excluded from political power under the NEP, the national bourgeoisie in China are also excluded from real political power with no capitalist membership in the Central Committee of the CPC. Lists of the wealthiest people in China are often called the "kill pigs list" as about 17% of these capitalists according to one study end up in court, jailed, and some being even executed with about 14 billionaires being executed in China within just 8 years.

The CPC also implemented a form of workplace democracy through staff and workers’ representative congresses that allow worker participation in management decisions and these institutions exist within all state-owned enterprises and even parts of the private sector (the staff and workers’ representative congresses in the state sector have more power though). The CPC can control its private sector through active management via quick direct interventions or more passively managing its private sector through its Communist Party committees within China's private enterprises, joint ventures, and foreign enterprises that influence management decisions to be more aligned with Communist Party goals. 5-Year Plans also still exist with directive economic planning being retained for certain strategic publicly-owned sectors of the economy while indicative planning has replaced directive planning elsewhere.

Regardless of whether we label China in its current economic state as socialism, market socialism, or state capitalism, it's a massive mistake for any leftist to disavow China as simply "capitalist" as it dismisses how fundamentally different China's economy is from capitalist economies and strengthens the fallacious capitalist poverty reduction narratives of neoliberals like Steven Pinker whose arguments rests almost entirely upon China's progress on poverty reduction (global poverty reduction without China's poverty reduction numbers has largely stagnated throughout the capitalist world). It also ignores the important lesson that socialist projects are sometimes going to be forced into making strategic retreats due to capitalist encirclement and imperialism as we've seen with the Soviet Union under the NEP, China, Vietnam (Vietnam has a nearly identical economic model as China as it faced similar material conditions and was forced to restructure economically to have access to international capitalist markets), and even Cuba to a lesser extent. And holy shit my response was too late and way too long.