Stock corporation, even if flawed, are accountable to their stock holders at least to an extent; thus your point
> Private companies are accountable to no one
clearly does not hold. Corporations, of course, can also be steered and course-corrected (shareholders meetings).
Which seems to just devolve to "the lizards listen to whoever/whatever has money" at the high levels where the number of voters is very high.
2. The 'voting' and 'steering' in a corporation is also completely dependent on money. The value of your 'vote' is proportional to how much money you have. This isn't a democracy or some sort of equal system that will converge on serving people, it will converge on serving money. I'm genuinely baffled at how "you get one vote per person" and "your value and voting power is directly tied to your net worth" are in any way comparable. You and I have zero effective power over them, and always will.
It is not, eg. Zuck didn't control Facebook because he was a priori rich, he became rich because he controlled Facebook in a successful way. He gained those shares and that control with his skill and labor (and maybe one symbolic dollar or something).
Suffrage*. Not personhood.
Corporations only exist as a legal construct of other entities. Absent government, they wouldn't be corporations since there'd be no law to create them.