You are totally right. The problem isn't zqthat such a change from within the system can only happen from a position of immense power. So to actually fix these bugs you need to
Have enough power to change the constitution
Have gotten that power through the current system
Be so dedicated to change the system that you are willing to risk all that power for the change, because any meaningful change means that the systems that brought you to power won't work in that way anymore.
Now, to make matters more difficult, representative democraties usually spread that power over hundreds or thousands of people. So not only you need to fit the bill above, but also the top few hundred politicians in your country need to agree to potentially losing their power.
So what tends to happen is the opposite: Politicians amass power and make it harder and harder to replace them, until a war/civil war/revolution happens and the next crowd tries to make it better.
The US has had centuries to concentrate power, contrary to many European nations that were re-founded after wars in the last century.
So unless the US as we know it collapses, there won't be significant change to the better for the political system.