I feel like people here underestimate how much the GOP is living on the life support of gerrymandering, restrictive voting measures, and packing the courts. Even with all of that they still aren't doing all that well. If all three of these elements ceased to exist the GOP in its current form would not be a national party but for occasionally winning the senate because it's essentially a natural GOP gerrymander.
I would argue a lot of it is fortunate political geography at this point in time. The fact that you have FL OH and TX all vote ~10 points to the right of the nation, and the small state advantage in the senate. Even in state legislatures, Democrats benefit from political geography overall, but the GOP has it in virtually every swing state outside NV, AZ, and TX.
As for the House, that was a large part because of redistricting control last cycle, but now it’s far more balanced.