Add a bit of firming and you can. Or just accept a tiny bit of fossil fuels. Don't let perfect be the enemy of good enough.

We still need to decarbonize agriculture, chemicals, aviation, shipping, heavy industry, construction and so on. Most of which use either chemical energy carriers, or fossil feedstock.

Siphoning off a tiny bit off that for grid firming duty is trivial. Or do sustainable biofuels from food waste and so on.

Which is also what the system studies lands on. Finding that adding new nuclear makes it far more expensive.