Well, when I was learning about economics being 8 or 9 year old, it seemed for me how it should be.
A person or a group knowledgeable in some area find a bottleneck, some problem to solve, start a company, it grows, it becomes big. Then the next generation is what they pick for leadership, and picking people is always worse than the evolutionary mechanism of a company finding some bottleneck to be widened being gunshot faster than the rest. Then they pick their replacement. And so on. Eventually it dies, but since technologies are patented, they do not become actual secrets, only commercial secrets, and by the time a company dies the patents expire, so everybody can replace it for the humanity.
The niche that company discovered thus becomes competitive.
In our world, if patents would expire as fast as they did initially by design, these big companies would already be dead.
But they've bent the rules to make patents virtually eternal and thus big zombie companies are strangling the humanity.
The system wasn't bad, but eventually power changed it.
You are missing economies of scale. In most industries these create a significant barrier to entry. The patent may expire but the equipment is still expensive.
Sounds similar to what happened to Boeing. Once ran by engineers now ran by people suckling the teat of board members. Quality goes down, profits go up for these assholes.
Intel fell behind on chip manufacturing while the CEO came from that department.
Allegedly because their strategy was too ambitious at the time, or at least that was the official excuse at the time.
So your summary is not entirely fair.