It’s not so much that the electorate has become so much more ignorant but that who is allowed to vote (who is included in the electorate) has changed so drastically from the time of the founding.
From Wikipedia...
“The United States Constitution did not originally define who was eligible to vote, allowing each state to determine who was eligible. In the early history of the U.S., most states allowed only white male adult property owners to vote.[1][2][3] Women could vote in New Jersey (provided they could meet the property requirement) and in some local jurisdictions in other northern states. Non-white Americans could also vote in these jurisdictions, provided they could meet the property requirement. Freed slaves could vote in four states. Initially, men without property and women were largely prohibited from voting.”
Think what a different country we would have today if those rules still applied, i.e. if the “system” hadn’t been changed.
A senate of the states was designed to not only represent the states, but to keep a lid on the mob over in the House.
Instead, we've been subjected to the equivalent of three-term congressmen with enormous egos whose interest begins and ends with popular reelection instead of looking out for their states.