> want Belgium to go all-in on renewables
I want everyone to go all in on anything that isn't a fossil fuel. The problem with gatekeeping new energy is upgrading the grid to accomodate wind and solar, and waiting for batteries to be delivered, creates a gap that gets filled with fossil fuels. The pragmatic solution to the energy problem is all of the above; joined with climate change, it's everything above but fossil fuels.
Depending on the country's situation, you might have to use fossil fuels during the transition, that's alright. But the transition is non-negotiable at this point.
IIRC those old Belgian reactors got in the way of more renewables for some time. They provided a very cheap base load that seemed hard to modulate, which meant that even cheap renewables couldn't really compete on price. If I understand correctly, newer nukes can more easily modulate their output, which would be useful at night or on days without wind etc. Gas peaker plants currently fill this gap.