More people most of all means more people who can and necessarily will break things, which are very hard to repair. Like climate stuff. The chance of having some super geniuses, that we would otherwise have missed out on, who then repair a broken climate is ... vanishingly small.
I am more looking at the long term effects here, because I care about future generations too.
Another problem with your view is, that you are totally disregarding other species on planet Earth, which are going extinct or become endangered species in this very moment, in which we enjoy that our "condition is better than ever".
I don't think we're living on credit forever as productivity/technology has improved over time.