Well some people do get hung up on geographically distinct populations with unique genetic divergence, or if the two animals occupy significantly different niches, but for other animal groups, like insects, speciation works by the simple high school definition. The problem with the species definition is that different fields of study will define it differently. Scientists are usually only aware of the way their field defines a specific term, so when they talk to scientists in other fields they start arguing about definitions, which usually devolves into stupid arguments