They aren't “optimistic”, nuclear simply doesn't emit CO2 directly, and indirect emissions are dwarfed by direct emissions of fossils fuel plants.
> What can and is being done is to replace coal as quickly as possible and that is happening.
It has been happening for the past 13 years, and there's no end in sight. We'll be able to have the same discussion in 13 years with only marginal progress (maybe they'll be around 200g/kWh at that point if we're being optimistic…).
> and even more so by France having to shut down too many nuclear reactors for repairs - German coal had to fill part of that gap.
And so what? French nuclear has been filling the gap for defunct German nuclear for more than a decade now … And Germany could have filled this gap with coal even if they had much less regular coal use thanks to their nuclear.