There's a long running historiographical debate about the relative influence individuals have over the ultimate course of historical events compared to systemic factors
For many years, it was popular (particularly in revisionist circles) almost entirely to deny individual agency and to rely instead exclusively on systemic arguments which highlighted the power of geography, ecology, culture, technology, and other complex systems to shape human events. That revisionist approach emerged partially in reaction to the near universal overreliance of prior generations of historians on the so-called "Great Man" theory of history, which assumes events are largely attributable to the decisions of a select group of politically powerful individuals. Nearly all of those individuals happened to be white, male, and wealthy, and thus Great Man history suffered not only from blindness to systemic factors that can shape events, but also to the experiences, contributions, and agency of anyone who was not rich, not white, not a man, or even simply not politically powerful enough to count. In other words, they ignore nearly everyone who has ever lived.
Although academic history has long since moved away from the Great Man theory, it remains a popular trope of low quality popular history books, and increasingly it has become clear that purely systemic, revisionist approaches with no consideration for the effects of individual actors are also inadequate to explain historical events.
Sometimes systems are more powerful than people, and no amount of good will or effort is going to fix a problem. The Vikings abandoned Greenland during the Little Ice Age because they had no way of controlling the climate or adapting efficiently to the changes. The climate system was more powerful than any individual Norse settler or group of settlers could ever hope to be.
Sometimes systems are weaker than people, and leaders can bend them to their will. After nearly 1000 years of independence from secular authority and mostly uncontested religious domination in England, the Catholic Church in the 16th century formed an incredibly powerful institutional system of religious control built on vast endowments of land. It was by and large extremely popular with the common people and historically served a critical role in bolstering the king's position by promoting a respect for hierarchy that naturally encompassed both their own elevated status as priests and the position of secular authoritarian rulers, who ruled as God's representative on Earth. Despite the Church's enduring local popularity, its immense wealth, its deep connections with the broader Christian world, and the powerful hold fear of excommunication and damnation had on most Christians, King Henry VIII managed to completely transform the institutional, legal, and property-managing system of the medieval English Catholic Church, sundering it entirely from Rome, depriving it of essentially all of its land holdings, and subordinating its institutions entirely to royal authority. And he accomplished this in a shockingly short period of time, only around a decade.
Why did Henry decide to throw his lot in with the Reformation? Was it because he saw the injustice of monks, priests, and friars siphoning off so much of his subjects' wealth to Rome simply to subsidize the already luxurious and decidedly un-Christian lifestyle enjoyed by the pope? Not at all, in fact in the years before his marriage to Katherine of Aragon soured, he wrote a book defending the pope, who promptly named the king Defender of the Faith in gratitude and recognition of his scholastic achievement. Did Henry instead recognize an opportunity to enrich himself? Probably not, the evidence suggests he wasn't that savvy about money, but luckily for him, he had Cromwell to take care of the pounds and the pennies. Ultimately, he just needed a divorce. Because if he failed to produce an heir, the danger of civil war would be intolerable, and Katherine was clearly beyond her childbearing years. But the pope wouldn't give him one, and Henry was a raging narcissist willing to burst through any boundary in service of his own ego, even risking his soul to break from Rome.
So individual idiosyncrasies can also affect the course of events, we can't just look at systems, and we can't just look at individuals, we need systems too. The relative influence of each over how a complex institution like a justice system develops is a highly contingent and fact-specific analysis. Sometimes the climate can push winters to be too cold even for the hardiest settlers. Sometimes an entire nation's centuries-long, enduring religious beliefs and ideologies can depend solely on the whims (and lust) of a single egotistical dictator. And sometimes when such a basic function is this messed up, you might actually find that there are indeed a limited number of individuals responsible, and that replacing them with competent or less malicious individuals will actually solve the problem.
That's the trick though, and where the systemic and individual-focused explanatory variables start to bleed into each other. If it is systematically impossible to find good people to staff these institutions, then yes merely swapping out individuals will not fix the situation because by definition you are swapping out bad people for other bad people. However, I seriously doubt that it is impossible to do so in this case, because even if the US justice system is messed up and broken, this is about the most messed up and broken that it gets. I think it's fair to say that 99.999% of the country does not experience systemic justice problems to the same extent as Maverick County, which is why so many people are reacting to this story with justifiable shock. So even assuming ad arguendo that it is systemically impossible to find truly good people to work in law enforcement or the judicial system, we know it's at least possible to find better people than they have in Maverick County.