The reason why anti-aging is hard is that humans are already very long lived for a large high metabolism mammal. As a result it's likely that evolution has already picked most of the low hanging fruit in humans. We're already optimized for decent longevity.

This is why you see so many promising longevity studies in mice that don't replicate in humans. Mice are not particularly long lived compared to humans, so it's much easier to extend their life spans.