True but they do change to mirror the people behind them. Look, the country was founded on the principals of all freedom and liberty for all, and we are still working at accomplishing this 230 years later, because virtually all of the people in government were sexist white supremacists. As those people died off, or were voted out things begin to change. Sure 45 represents some regression, but even he is a reflection of what the people want.
Now that most reasonable people know he was a mistake, I'm confident to predict he will be booted out of office in 2020. Things will start to improve, for everyone, after 2020 for everyone barring a Russian invasion, another pandemic, or some other calamity.
As far as your example with police departments. They have changed a great deal -- even in my life time. It was not long ago when minorities and women were excluded from the ranks of police officers. Today is a completely different picture in places like NYC. Improving is a work in progress.
The cry for defunding the police is getting louder today. Cities recognize that these departments need to be completely rebooted. Police department need people reflect the values of the communities. The Police Department in Camden NJ did this: they fired everyone and hired the people willing to serve the communities and indications are that it was been an unqualified success!
Institution bend to the will of the people they are intended to serve. They must, or they will collapse.