Your tldr does not follow from any of the things you wrote above. Considering current energy densities it doesn't seem unfeasible to me to build that storage. And I was honestly surprised how little space this would have taken back in 2020, not to mention that, again, this has been reduced by about 4x today. And it's going to go down further. Your only argument here seems to be space and I don't see that as a big problem. A few soccer fields worth of land distributed in the vicinity of each bigger city doesn't seem like a lot to me.

I do see your point that it is in the interest of fossil fuel to stop nuclear power from replacing them. But I don't agree that we won't be able to build an energy grid without fossile fuels. I believe we can have a grid without both of these technologies.

You seem to be influenced by the "well we won't do anything until we are already burning" mentality which is coincidentally pushed heavily by the fossil industry. It's meant to defer people from believing that change is possible and taking action so we all stay at home and bicker about how cool it would have been if we started change 20 years ago.