Most work is unnecessary, bureaucratic and consumerist bs. Still many people are unemployed. Automation is held back by unions who fight for their right to do even the crappiest work, like mining. Inhabitable land is overcrowded. Less people is definitely net positive. Surely the economy might take a hit, cause it requires steady growth, but while that is bullshit in its own, we could still have growing economy with declining workforce, everyone would have to get very wealthy then.