You become accountable to an entire mass of people who don't help you do anything, don't bring anything to the company,
They bought shares. Originally, shares were issued for the purpose of raising money to accelerate a company's growth.
Lately, companies seem to be leaning on numerous other finance streams, instead. So, the point of an IPO is now just to give its execs and VCs a payday.
A big benefit to customers, workers, the economy, and society is that publicly-traded companies are required to provide a substantial degree of transparency. It's also significant that shareholders get to vote on major decisions. In the case of a private company, there's none of that. It's basically just a black box.
As for the downsides of being a public company, I think Qualcomm stands as a good example. Activist investors forced them to kill off numerous internal profits and force the company to prioritize short-term profitability. They can also push for (more) dividends, which deprives companies of capital they could otherwise invest in future growth.
Though I'm pretty negative on dividends, from a company's perspective, I suppose they do serve a function in supporting wealth redistribution. Otherwise, I guess you'd just have all of the profits going a tiny class of billionare owners.
I know we shouldn't criticize the system, but it is what it is.
Huh? Why shouldn't we criticize?
Everyone knows it's not perfect, and more discussion of its positives and negatives can (theoreticaly) lead to fixes and improvements.
The US economic system wasn't created by divine hands, and it ultimately exists to serve pragmatic ends. We shouldn't forget that, and shouldn't lose sight of where it's doing well and poorly.