There's two issues, success rate (about 5%) and time ... even if it is successful in humans, it will be 5 to 10 years before it's available (and 20-30 before it's affordable)
To be fair, this same realist perspective seems to suggest humans would not have been capable of developing a COVID vaccine for 5 to 10 years; yet, they identified the virus and authorized vaccine use within eight months.
Not to diminish the accomplishment of rolling out the Covid vaccine in such a rapid timeframe, but… there was something like 40+ years of research into creating mRNA vaccines that laid the ground work.