They can use a referendum to overturn a map in Ohio. However, enough minority Democrats defected on the new revised maps (as opposed to the first attempt) to get a 2/3 majority that prevents a ballot measure. That's why you saw a new redistricting proposal instead of a referendum. A more well-written initiative certainly would have done better, let alone a better campaign. Issue 2 seemed to have an abnormal amount of nonpartisan/independent opposition. I think the forces that support redistricting reform should take up Republican Jon Husted's
proposal and put it on the ballot ASAP. There's no reason why any new redistricting amendment should not take effect immediately. With current lines as they are, almost all Republicans will oppose any new setup, even one that wouldn't take effect until the 2022 elections.
