As to nuclear reactors, there is that pesky problem of nuclear waste, still unsolved after fifty years, more from lack of political will than technology.

As to GMOs, haven't you heard that fertiliser was one of the biggest disasters ever for humanity, BECAUSE it produced higher yields of edible mass per acre and thereby led to the overpopulation and environmental resource overshoot that is leading to the end of technological civilization in our lifetime? That's all we need, another boost to yeild per acre—to accelerate the collapse of civilization. Population 10 billion, here we come!