Why both the Democrats and Republicans are so disliked

Just two political parties have long dominated American government. The 117th Congress had just two independent members in the Senate, who both caucus with the Democrats. It's been more than half a century since a candidate who wasn't a Democrat or a Republican won any electoral votes in a presidential election. But an increasing number of Americans are expressing their discontent, with a study [cite source here] saying that nearly 4 in 10 of them want more parties to choose from.