The author is saying that people living today are overly concerned about the environmental effects of experimenting with new technologies when compared with people in the recent past.
You, being a person living today, have just expressed that you are overly concerned about the environmental effects of experimenting with new technologies. That's not a criticism, we are all a product of the time we live in.
That's not to say that people in the past had no concern about the environment, it's just that they weighted the costs and benefits differently to modern people when comparing anticipated benefits for humanity against potential environmental effects.
The author correlates this different weighting with increased technological progress in the past. I think that is very hard to measure as it really depends on what you value.
I agree that you can list examples of people racing ahead to use new technologies and there being negative consequences. But what about all the times that humans raced ahead with new technologies and there were positive consequences? If we didn't race ahead would we be better off or worse off overall? When you delay implementing a technology due to concern about the potential side effects you make people worse off in the interim than what they would have been if you went ahead. We can never really know what all the consequences of our actions will be until we act.