I am not familiar with how much renewable generation Germany has, but generating more even if they have a small window of time where they have sun / wind - is cheap to solve (I am certain there are many structures where solar panels can be installed that do not have them), just like in the US or elsewhere. The the #1 issue is obviously storage - and there is so much research into alternatives to lithium-ion batteries that I am certain we will see a breakthrough in that area before we will see a breakthrough in nuclear - simply because there is so much more investment in it.
If it is Sodium Ion batteries or solid state state batteries, I am not certain, there is a lot of research into solid-state batteries simply because they are so safe for mobile applications (transportation) and they are very dense, but sodium-ion batteries have just gone into a commercial phase - so I would not be surprised if this will be the preferred medium for utilities to use for renewable produced energy storage.
https://www.arenaev.com/worlds_firs...ttery_production_line_goes_live-news-1101.php
Sodium ion batteries are not as dense as lithium ion batteries and at this point in time (very early in commercial availability) are a little more expensive, but the raw materials are readily available and cheap so you would assume that once more and more are developed and commercialized - they will become cheaper and unlike lithium ion, there is much less of an issue with raw material availability.
Solid state batteries are still in pre-commercial phase - but there is a belief that there will be multiple offering starting in 2024
https://www.cnbc.com/2022/06/06/solid-power-begins-pilot-production-of-solid-state-ev-battery.html
(I believe QuantumScape were supposed to already have commercial availability of their solid-state batteries, but I have not seen that, so let's assume that like Solid Power they are still in alpha/beta testing phase).
Of course, for large installations run by utilities you can use things like kinetic energy storage (pumped hydro or stacked big rocks up a mountain when generation happens, recreate the energy by sliding them down when you have demand) or pressurized air - so even if these other batteries technologies do not pan out, there are alternatives for energy storage that are no resource limited)
So in summary, no nation on earth has maximized it's ability to generate power from renewables, there are tons of untapped roofs all over the world ready for solar production. In addition, the issue of storage is one that is going to be solved - there are so many options to do that even if we run out of lithium ion (which frankly, is not likely to happen for a decade or two, it has not been researched as much as oil - and there are many deposits that can be found if needs be, the Salton Sea, for example has a huge reserve of lithium deposits that if/when it makes financial sense will be mined, in the US there is only one place where Lithium is mined (Nevada) - and I am sure more and more will be mined with time).
Let's also remember that all these EVs that the world is slowly moving to, at some point, when they are decommissioned, their batteries - even if they lost too much range for transportation purposes, are perfect for local storage in micro-grids, great for applications in residential homes or small businesses. Storage is not a problem that can not be solved and the world is spending a lot of money to research it.
Nuclear, as I said, unless a breakthrough happens, seems like a niche technology that is not likely to grow. It is simply too expensive.