What is a "blockbuster" drug? One that makes a lot of money for the various stakeholders or one that has a large impact on human health? I'm not sure I care too

What is a "blockbuster" drug? One that makes a lot of money for the various stakeholders or one that has a large impact on human health? I'm not sure I care too much about the former and it's not at all obvious how "level of confidence" would affect the latter. Yes, as a result of past medical progress it is more difficult to improve upon the current state of the art. But new therapies have to compete with existing therapies in the market anyway. If a new therapy can't outperform existing ones, what actual value does it have? Perhaps drug companies should think about solving problems that aren't already solved rather than bemoaning their inability to reap massive profits while reinventing the wheel or pushing minor formulation tweaks to renew their patents.