The amount of risk I'm willing to take depends on how bad the alternative is. And it's completely subjective.
If the danger (or pain) is great enough, I'm willing to do extreme things-- even really risky things-- to alleviate it. It's pure desperation.
If a fireball is chasing me down a hallway I might be willing to jump through a window, not knowing what's on the other side.
Similarly, I would be willing to try experimental mRNA treatment for something like cancer, but not for an over-hyped cold. The risk/reward in the Covid-19 situation is completely upside-down in my subjective opinion.