The value of those states was not in question when they threatened succession; they were important enough to fight a war over. Nor would many of the states have joined the union in the first place if not for this system, so America wouldn't have existed in the first place if you had your way. The entire country is premised on this compromise.
The centuries-old political climate in which the electoral college was born has little if any bearing on its utility for the modern United States. I doubt the only thing keeping rural states in the union now is leverage against abolitionists.
It's because tyranny of the minority means prevention against new laws, not the enactment of them. It's the safer path, generally not absolutely. A bias towards inaction.
Tyranny of the minority only means prevention of laws the minority disagrees with. That minority hasn't, historically, taken issue with new laws that cater to them.
