The term "Developing Countries" might have made sense once.
Today it's impossible to make a clear distinction between "developing" and "developed" countries.
In 1950, most of the so-called "developing countries" had more than 5 children per women and less than 50 years of life expectancy.
Today, in most of the world, women have less than 3 and life expectancy is over 65 years.
Any attempt to divide the countries of the world into two groups, such as "developing and developed countries" will be an over-simplification.
Click play on the graph in the link below to see how the world has changed since 1950.