You're pessimistic because you start from the wrong idea, and your phd professor does the same mistake. The idea that we need 100% understanding of the process before finding a way to treat/reverse/cure is not true.

If you start reading about the medicine we're currently using you'll notice a trend, more precisely a lot of the chemicals that we're using are not fully understood and we don't know for sure what's the mechanism of action, we might know the receptors they bind to, and we have some theories that sound plausible enough. That does not stop us from using said medicine, because we observe the effects and we conclude that it's useful.

Same with anti-aging, there's a big chance we'll find something that works, we'll observe the effects and we'll start using it before understanding 100% how it works and describe each chemical reaction.