Not only is this all by design, but in many countries, the "free mandate" - i.e. the notion that the politician can say A before the election and then do ~A after - is even legally codified. In theory, this is supposed to allow the elected representatives to apply their own judgment based on nuances of the moment instead of pandering to the mob. In practice, it means that your representative is free to pander to people other than those they "represent" while still claiming a public mandate based on the votes received.
They're just praying that one will be moderately less terrible than the alternative.
There's never an option to say, "No, none of these power-hungry psychos should get to make this set of decisions on my behalf."
We elect representatives at every level of government. In a country of 335,000,000 people a slow moving central government is a feature. If you really want to make a difference pay attention to your city council.
Note, by the way, that I'm not claiming that changes don't happen in this system. What I'm saying is that changes happen when the ruling class is convinced it's time for them, not when the populace as a whole is - and no amount of voting changes that.
The fewer people each representative represents, the closer it is to an actual democracy, which is why city councils etc generally work better (although they are still far from ideal and have the same fundamental problems I described). But the nature of modern politics weaves local issues into broader ones on higher levels, and what ought to be local politics increasingly becomes national.