That's not actually the reason—eradication efforts have not been avoided on this basis, indeed, mosquito eradication has long been a central pillar of efforts to control malaria. The reason for trying something else is that eradication efforts have rarely been completely successful and mosquitos are getting better and resisting them from the reproduction pressure imposed by the massive, sustained efforts at eradication, not because eradictation is something people want to avoid because “genociding” mosquitos is seen as undesirable.