This is a religious stance, like many worlds theory or any religion you know. You can’t prove it. You can spend your live chase evidence, but there is no experiment to prove it. So, go warship if that’s your thing.
In 20years we will have fusion. Then everything solved. That's what I learned when I was a child in the 1960s. It a truth renewed every year.
We may need gen IV fission for one reason, and one reason only: to get rid/at least reduce nuc waste and weapon plutonium. Lets get that shit off the planet, its as bad as CO2