Just like there are many diseases that can't be effectively treated, there are many things that can't be effectively researched.
I would guess that if there was an effective way to research the reversing of aging billionaires would be on it out of self interest. But if we have no clue how to approach a problem it isn't clear that spending money on it will help.
To put it another way, even if we could invent a cure for aging one day, if we posit science is 500 years away from such a cure, and billions of dollars would only advance things so a cure would be 450 years away, no living billionaire would be incentivized towards that research.
I tend to see those platitudes like "life has no meaning without death" are a form of self comfort, since we are stuck with death.
Still, humans wouldn't exist without death, since the evolutionary process of natural selection that created us cannot or could not exist without death, so it isn't entirely wrong to consider life and death fundamentally linked.