The founders of the US were well aware of how disastrous strict democracy was for Athens. After Pericles died in the smallpox epidemic, the mob veered back and forth supporting demogogues who eventually frittered away any advantage the Athenian League had over the Spartan alliance. In fact, the war with the Spartan league was started foolishly following the democratic mob impulse for "glory". They had a good thing going and fucked it up because cooler heads were ignore by the rabble.
Also, don't forget that only free male citizens had a say in the government, so woman and the considerable population of slaves (essentially, the working class) had no say. Something the modern GOP would be drooling over being able to replicate in this day and age.