That job description is found in Article I of the Constitution, and it’s hefty. It includes managing the country’s finances, e.g., budgets and debt, ratifying treaties, and passing laws. Congress can also impeach (remove from office) a president who fails to fulfill executive obligations.
When Congress fails in it’s responsibilities, the country can experience financial and legal crises, lose credibility internationally, and find that the president is assuming too much power. When Congress fails in it’s responsibilities, it’s up to “We the people” to replace underperforming senators and representatives with people who will step up to the job.
Unfortunately, while it’s easy to say “vote them all out” you have to remember that you’re replacing career politicians with more career politicians who probably won’t behave any differently in Washington than the ones you vote out.
There are two ways to make Congress more responsive to “We the people”. One is to limit campaign contributions from all organizations and individuals as well. I include individuals because of certain wealthy elitists who think their money gives them the right to tell us “little people” how to live. Money may buy power but it doesn’t buy rights. The other is term limits, around 18-20 years total between the House and the Senate. Term limits would restore the concept of citizens serving their nation rather than career politicians serving their party.