Nuclear tends to share this. Most nuclear reactor technology is not optimized for rapid swings in production. A reactor is a very expensive thing to not run most of the time.

The two technologies aren't terribly compatible. The first tend to be intermittent (not great for on demand needs) and the second are best suited for base load.

What you need is something that is relatively cheap to maintain, and can be ramped up quickly. This is where you typically see natural gas peakers in a fossil-fuel based system.

Wikipedia summarizes these well:

https://en.wikipedia.org/wiki/Peaking_power_plant

https://en.wikipedia.org/wiki/Base_load

For peaking demand you need something that can store energy and can adjust to load rapidly. Batteries do this (I include mechanical solutions as batteries, e.g. a flywheel or pumped hydroelectric). Natural gas plants tend to fill this role now. These are not the only options, just common examples.

And with intermittent energy sources, there are additional problems. We only get energy sometimes. We want energy always. It basically inverts the idea of base load and peak load sources. If your source is intermittent, then you do want to be able to over-produce at certain times, with an ability to capture the energy. Think batteries, but know that they need not be chemical batteries. Energy storage can then cover the valleys of production or the peaks of demand.

Add coordination to the challenges as well. Much (most?) solar is distributed. It's much easier to ramp generation up or down in a few centralized plants. If every home has a solar panel array, then you need to be able (either at the local or the grid level) be able to store excess energy or turn off production.

None of this is insurmountable, but there are many challenges that are non-trivial by nature and some that are difficult d/t the way energy grids are typically set up.