Why is it unsustainable to rely on infrastructure investment to stimulate GDP growth?

This view has limitations. A distinction should be made between developed and developing countries. In developed countries, of course, we can't rely on infrastructure investment to boost GDP, because the infrastructure of this construction has been completed, but it is completely different in developing countries. There are too many infrastructure debts in these backward countries. It is no exaggeration to say that if we invest in construction for 20 years, we may not reach the level of developed countries. Then, can it be said that it is "unsustainable" to play a role in stimulating GDP growth for 20 consecutive years? Of course, it will continue to stimulate the economy. Therefore, according to my experience in the provincial industrial economic management department, it is still a reasonable choice for most developing countries in the world to rely on infrastructure investment to stimulate economic development within a few years. Even in China, behind the GDP of 74 trillion yuan, the annual infrastructure investment of 60 trillion yuan is absolutely indispensable. Moreover, the annual appreciation rate of infrastructure investment is still around 5%, which shows that it is quite sustainable.