Maybe you could think about it like that: capitalists are the class that, in order to exist, is forced to continuously take capital and invest it to make profit or they are outcompeted by other capitalists. It’s not that they are all evil or “corrupted by power”, they are not just incentiveized, but forced to act in destructive ways: steal surplus value from workers, increase exploitation above what people can take, chase profits on an exponentially expanding mass of capital in a finite world destroying the planet, cause a crisis about every seven years, cannibalize their own state and infrastructure that they rely on for short term profit, etc.
They inevitably run into these contradictions due to living on a finite planet and having to put individual interests above all else while the modern economies distribution of work and global value chains absolutely require working together.
What you are worried about is real too in a way, but it’s not a class. In a socialist state, a managerial part of the working class is not forced by competition to continuously pursue personal gain, but some of them still might become corrupt and do so anyway. At that point, they have betrayed the working class and they might even do so in favor of real capitalists domestic or abroad who haven’t yet completely disappeared as a class. It’s a possible problem, but other than the class conflict between workers and capital, it’s not inevitably the dominating principle of society.
Rather than worrying about a hypothetical future betrayal of fellow workers in thriving and prospering China, we should focus on how many western workers have already often betrayed the rest of the global working class and continue to do so by supporting terrible imperialist wars, mostly in turn for cheap goods at Walmart.





Also no apology yet for continuing to materially support the ongoing genocide in Palestine by white fascist colonizers. Or for the 27 million Russians killed in WW2, the largest group of victims by far. Or for murdering over a million socialists. Or for financing and arming the anti-communist genocide in Indonesia in 1965/66. If Germany is anything, it’s consistent. Not one bit less eager to commit genocide today.