Well, the US has divided its authority into houses to maintain a balance of powers, so that no single authority can dominate the decision making process.
The executive is charged with being the head of state, namely a single person to negotiate treaties. The senate, or the "upper"/"elder" house, must ratify those treaties before they become law.
The congress, the "lower" or "junior" house, was meant to deal with day-to-day issues of the younger folk, those with a future.
In general it was originally decided that any two of the congress, senate, and executive are needed to make a law.
The judicial branch is intended to resolve disputes based on judicial principles. Except where there is a legal vacuum they cannot create law ("stare decisis" / "ratio decidendi").
It would that the balance of the division of powers is mulching of late, and I agree it is a problem â" not just on principle, but in sticking with the design choices of the founders of the United States.