When a company IPOs, ownership of that concern is split up into x pieces. The company has some amount of value, which is divided among the shares. As the company increases in value (hopefully), so do the shares. That is the reason why investing in a company is different than baseball cards. Baseball cards only appreciate in value due to changes in supply and demand, whereas a business can actively create value. There is no need to delve into weird counterfactuals or discursions on what the idea of partial ownership "means".
If a business's value can't be plausibly enjoyed by the shareholders, then the shares really are no more than baseball cards.
So far, the ways for a business's value to be enjoyed by the shareholders have been broken down to (a) dividends, (b) stock buybacks, (c) the ability to take control of the business, (d) the ability to sell stock to someone else attempting to take control of the business, and (e) claiming a share of the business's assets after dissolution.
(e) is right out--for a company that's doing well at all, their market cap is higher than the value of their assets less their liabilities, and a company doing poorly is certain to become insolvent before being dissolved. This is almost an intended feature of limited liability: the company can borrow itself to death, and the worst case scenario is that the stockholders get nothing.
(a) and (b) are stipulated as part of the original question--if the company doesn't issue dividends or buy back stock, of what value is the stock? Which leaves (c) and (d), which can be plausibly ruled out by having one intransigent party holding a majority share.
When a company IPOs, ownership of that concern is split up into x pieces. The company has some amount of value, which is divided among the shares. As the company increases in value (hopefully), so do the shares. That is the reason why investing in a company is different than baseball cards. Baseball cards only appreciate in value due to changes in supply and demand, whereas a business can actively create value. There is no need to delve into weird counterfactuals or discursions on what the idea of partial ownership "means".