"The purpose of a corporation by definition is to maximize the bottom line for the shareholder."
No, the purpose of a corporation is to efficiently organize work.
Fundamentally, corporations, and the entire economic system, exist for only one purpose: to create a better human society. Profit is the incentive to get them to work for the greater good, but it's not the end-goal. We've temporarily lost sight of that, but sooner or later we're going to have to redefine corporations so we can keep the good (competitive drive), and discard the bad (profit at the expense of humanity).
Personally, I would be very interested to see minimum holding times for shares (incentivizing long-term behavior), and maximum lifetimes for corporate personhood (corporations should all die at some point, just like other people).