Humans are like any living thing: they grow until limited by a limiting resource, whether that be a nutrient, space in a niche, or a waste product. In our case, technology has helped us remove one limiting resource after another. But it can't help us with our biological drives to procreate. Ultimately it may be our waste products which limit us.
"Development" has tended to limit population growth somewhat. But it has also caused resource consumption to explode. Fewer people, but more consumption per person, still equals environmental disaster.
Is energy the only limiting factor? If we have limitless energy will we be home free? Depends on your values, I guess.
Personally, I see the evil as being the whole definition of "economic growth". Economic growth is a pyramid scam- a geometric series, fundamentally unsustainable. It rewards consumption, which is the very thing we've got to get a handle on if we're going to survive as a species. The sooner we learn to live without "economic growth", the better off we'll all be.