Constitutions are supposed to reflect supreme will of the people, not by just a bare majority. Amendments should be hard to pass for that reason.
That said, I’m arguing only the percentage threshold – the will of the people, all people in the jurisdiction considered equally for this purpose. The “signatures from all counties” portion of this Ohio issue violates that by giving greater weight (and impedance) to rural communities where organization is hard and populations are smaller. It would take only one county with low turnout to block serious consideration of meaningful issues that affect the entire state.