I would argue that Demographic Transition is true because it is basically the main concept overtime even though it is from so long ago. There might be differences if it was done again but the thing is that now it wouldn't be to easy to do it because there is less differences now and it has reached the 4th stage and probably passed it if it was extended. Also it is modeled properly but it should just be compared with actual rates of population today. The population differences in the model through time are also a little off because depending on the time and the events that happen through time the population can differ. This is also implied to death and birth rates.
Even though there is a variety of events through time that take place and cause great differences it doesn't mean that every single place in the world is the same. So in different areas since there are different events there are different demographic transitions. So you really can't rely on them thoroughly but they could be used as the bases of an idea. Maybe in one place there was a baby boom after war but in another most of the babies died and had problems do to war radiation.
You also have ideas such as those that in one place they practice certain religions that only allow certain amounts of kids per couple. So not just this but when there are to many humans like in China they start picking out what to take either girl or boy. So yea they practically kill the children. There are also other reasons why they aren't so accurate and should only be used as an idea. The model is good to compare to but what about all of those that aren't recorded on there.
You also have to notice that even though it is not the best thing to look at you can use it to compare the actual information of some places and get a close average of what the population is. Sometimes it is better to use the relevant information but it takes time and research to get relevant info. It can take years to complete one of these of an actual situation in a country. So even though it is based mainly on North America and it is an example depending on the events it is a good control. Another thing that creates a big difference is the development of certain places.
