It might seem that way, but minimum and maximum power demand are generally so far apart when you include seasonal differences, solar and nuclear need about as much peaking power to supplement each other. That’s why even with huge exports Frances nuclear power stations hover around 77% utilization where US nuclear can hit 92%. Nuclear can clearly play a role, especially near the poles, but it’s just really expensive.

In the end Ontario is in an unusual situation that stops working as the rest of Canada scales either nuclear or wind power. It’s working for them and their electricity is mostly carbon neutral, it just does not scale.

PS: That’s not to say nuclear can’t scale to 100%, nuclear subs make it work with wildly swinging demand. However, low capacity factor directly results in higher costs.