The senate has always been a problem for democrats. But you can see why they chose a different voting system for each house.
It is compounded by the fact that Washington DC also can’t elect anyone to the House or Senate which is a further problem for democrats, as they would gain another seat there too, as Washington is usually Democrat leaning.
And yet the Democrats cling onto the 'across the aisle' mirage, when they have been repeatedly shafted by the Republicans, instead of sorting out the voting inadequacies (see also the Electoral College, which is a total farce).
In many ways, America deserves the fiasco it's brought on itself by clinging to the pretence that they are exceptional and that their Constitution is some bible-like text, rather than a cobbled-together series of compromises to try to appease slave owners and gun-totin' ranchers who stole all their land from native Americans.