I think he's saying that research is far behind on fission because it hasn't been supported, and since it takes so long (and so much money) to spin up new plant

I think he's saying that research is far behind on fission because it hasn't been supported, and since it takes so long (and so much money) to spin up new plants, that it's better to invest that money into renewables. That's the impression I got. I don't know enough about the specifics to say if I agree with it or not. The opposition to nuclear was so effective in the 70's and 80's that they shutdown any further development on it. That's probably why you don't know anyone opposed to it. It's not really even an option anymore.