There are several lines of storage research that only need to be ramped up to mass production at this point. Since stationary storage doesn't have the weight restrictions that electric car batteries do, there are many different viable options. Flow batteries, sodium batteries, pumping water uphill, big tower of concrete blocks on pullies, hydrogen electrolysis, big ceramic block that gets hot. Some will work wherever, others are only viable in certain situations, but there are many options and we only need one of them to work at scale.

When nuclear tries to make improvements, it tends to do one thing per decade. If it fails, wait another decade to try the next thing. Last decade, it was the AP1000 reactor. It was hoped it would make a single, repeatable design that would avoid the boutique engineering that caused budget and schedule overruns in the past. Didn't work out that way. This decade, it's Small Modular Reactors. The recent collapse of the Utah project doesn't give much hope for it.

Even if it does, it won't be proven out before 2030. We'll want to be on 90% clean electrical technology by then if we have even a hope of keeping climate change at bay. There is no longer a path with nuclear that could do so. Given project construction times, the clock ran out already.

Pumped hydro works well for storage, although it basically has the same problem as hydro power - it's only available in places with water and elevation changes.

If every home was a battery instead of an armory that would be a really cool redundant storage infrastructure. Likely not financially viable compared to centralized storage but it would be kind of cool if their was no immediate central reliance on power so any interruption in power generation could withstand say 1 week of storage reserves nation wide before outages started trickling off to support say hospitals, heating above 40 degrees, etc. Entirely too complicated I’m sure but just a neat thought I had after reading your comment.

Don't forget power companies can also work with smart thermostat manufacturers and car manufacturers to implement demand side tweaks to reduce power consumption. If they need to drop demand by some number of megawatts, they can adjust everyone's thermostate by 1 degree temporarily and easily meet that need, or slow electric car charging by half a kilowatt. As long as there's a manual override for users who need to charge right then or need to change the thermostat right then, this can easily make a significant dent in the variability of the grid with renewables

Even current lithium-based battery storage is already cheaper than nuclear.