There are more than enough resources on the planet. There are NOT enough resources for everyone to live like Europeans and Americans. But the simple fact is you don't need to live like that to be happy. I have seen families of 9 people living in a 1 bedroom apartment and happier than most Americans. Because they don't have so much stuff and they don't constantly see people who have way more than them to get jealous, or watch TV to see glamorous lifestyles that make them want more. Overpopulation is a question of WANTS not of needs.
No one is expecting this planet to be around 900 years from now.
You only have so much time to get affairs in order.