Because of the long build-time, you can buy the batteries 10 years from now, comparing to a nuclear plant that starts construction today.

Sure, but that's a shitty comparison, because I can also build 20 nuclear powerplants, and bring costs WAY down. And that's the thing. These comparisons are always "If we keep boosting X, and supressing Y, then X will perform better!". Yes. Duh.

Look at what China is doing. They've built dozens of plants in the past years, and have >30 under construction right now, with ~150 planned. They're building them for a fraction of the cost, because they're not completely reinventing them every single time.

It’s not like I am saying we should scrap ongoing constructions.

Fair, we shouldn't. But my worry is that even in 10 years, we're still going to be using lots of fossil fuels, and that will always be lower if we ALSO build nuclear. Or at the very least stop heavily opposing it.