I think your conflating Right and Left with Republican and Democrat.
They aren’t the same thing.
Both parties have been pro-corporate oligopoly. The Republicans, just more so.
Both parties have been catering to the same class of big corporate donors. The Republicans, just more so.
Both parties have been pro-military-industrial-complex. The Republicans, just more so.
Both parties have been pro-Israli genocide. The Republicans, just more so.
Both parties have shown a little movement toward economic populism. The Democrats, just more so.
They might not vote together on many bills. Because it would look bad to their respective bases if they did.
But they’ve both been pushing in similar directions on a number of topics for decades.