If the rolls were reversed and schumer was majority leader, I guarantee you the senate investigations of Trump would be exponentially more then what the house is doing now.
You are right - if roles were reversed and the Democrats had a razor thin majority, they would have no trouble advancing their agendas.
But the Democrats enjoy 100% support from the fake news monopoly, leftist academia, and the deep state bureaucracy. They get to lie with impunity and nobody challenges them. Decades of packing the courts with progressive judges....
Add to that the fact that the Democrat political model is based on wealth redistribution - vote for us and well give you other peoples money..
Its just not a fair comparison...they have the wind at their backs.
Republicans would probably need close to a supermajority in the Senate just to level the playing field.