France is phasing out 35% of their nuclear power in the next few years. With one exception[1], there are no new nuclear power plants in planning to replace any of the existing fleet, which will all have to be retired soon.
[1] Flamanville, which is 400% over budget and behind schedule by 11 years.
France made a policy decision to reduce Nuclear from 75% of 50%, largely a populist response to Fukushima, and the perception that Nuclear is dangerous, not green, etc.. It was a political decision, not practical. We'll see if they actually are able to meet that goal, but most signs point to no. Regardless, my point is France, a G7 nation got to 75% nuclear. Fear is the main reason other countries can't.
France started sufficiently early. I don't think we have the production capacities to switch over completely to nuclear power over the next twenty years (worldwide!). Building reactors takes a lot of time and is quite expensive.
I think right now renewable energy with storage and improved grids provides a better carbon reduction per dollar than nuclear. There is also a pretty big potential for saving energy, for example for AC. We need to be at net zero in ten to fifteen years. Building reactors takes a pretty long time. I don't think we even have enough qualified personnel to build the huge number of reactors we'd need to replace fossil power plants. Solar and wind seems like it needs less expertise, but I'm not an expert on this topic.
https://en.wikipedia.org/wiki/Nuclear_power_in_France