Just remember for much of the Post WWII era, Congress AND the Senate, and fairly often the presidency was held by the Democrats. It is only really in the wake of the post end of gold standard that the Republican party saw growth in it's numbers, basically in lock step with inflation. And I don't mean inflation approved by government made up CPI numbers that are doctored through changing methodology to promote as close to the supposed golden value of 2%, when if we look at most of history the real golden number for inflation was somewhere around 0%. The only benefactors of ending the gold standard were the wealthy. The major benefactors of free trade agreements were the wealthy. The only benefactors of shipping manufacturing to China was Western Governments hell bent on isolating the Soviet Union, when - that was hardly necessary, and practically speaking ineffective.
When people talk about gerrymandering, and so many other issues: What I start to see is a planned distraction, one masking a much older, deeper, and more fundamental truth that eats and rots the foundation.
Pure Fiat has been disastrous for productivity in the West. And that too has been disastrous for birth rates that again, fall in lock step starting with the oil crisis - and continuing on with disastrous fiscal policy, followed by export of good well paying blue collar jobs to foreign nations - removing the value creation from the local economy, and handing it to nations who politically are opposed to the wests way of life.
The only people who were wanting to change that in some way - got assassinated.
It is ABSOLUTELY functioning as designed. But you have to understand - Tyranny of the Majority; the threat of Religious Despots: Those two things were VERY MUCH in the minds of the founding fathers.
The argument is sometimes said as "they can step in" but in reality, that is up to the rules regulating how votes are cast based on state rules.
But you must first understand: The Founding fathers understood that Tyranny of the Majority could be a serious threat (see religious Tyranny and conflict that has lead to all kinds of problems and persecutions throughout history). It's complicated.
Now: If you want to argue that election reform is needed in the modern day: I ABSOLUTELY 100% AGREE. I would LOVE to see an abolishoning of first past the post, and party centric electoral voting - in favour of Ranked Choice Ballots where it all pans out through one single vote. But who benefits? Well: It's not the DNC, and it's not the GOP: SO good luck getting the constitutional amendment needed to make that a reality.
Thing is: We COULD start - at municipal elections, elections for small positions. That is the BEST place to start but odds are, even there, you are going to have the DNC, and GOP fighting it at every step of the way, because that is a DISASTER for party control over elected officials: After all, in a world of Mass to Mass communication, you don't need a big party to organize campaign drives - you can set up your social media posts, you can do a tonne of efforts and coordination remotely which means you can be out and talking to people basically anywhere in the country, and still be able to work to coordinate efforts directly.