(And in more modern views maybe you should worry about the other stakeholders too.)
Most shares in most companies I've seen have been owned or controlled by executives or by institutional investors (mutual funds, insurance cos., pensions) that tend to vote with executives' recommendations. Without high-level executive support, shareholders are free to do whatever they want, but the important ones typically don't want.
Since we believe that executives are the ones creating the wealth, it is just that the wealth flows out of the company and towards them. Executives giveth and executives taketh away.
I wonder how many people actually believe that.
Passive shareholders, well, don't participate on decision making.
Expect this feature to get worse with increased share of index funds. But not by much, because most people never were active anyway.
That's not true, fund managers vote on behalf of those shareholders, and not always go along with the board's position. See for example Vanguard's voting record: https://about.vanguard.com/investment-stewardship/how-our-fu...
You say "ruined", I say "fulfilled their ultimate purpose as disposable wealth-extraction machines enriching executives".
I totally agree that the stock market's design encourages short-termism. But this is entirely appropriate in service of the idea that heroic individuals are chiefly responsible for company outcomes.