Yes, nuclear reactors are terrible as peakers. I think that they would make sense mostly to put a floor under worst-case-minimum scenarios for renewable power generation (like "a week-long period of intense winter cold, far from the equator, while wind isn't blowing much.") In that scenario, there would still need to be some long-duration storage system like hydrogen in salt caverns but the storage reserves don't need to be as large as in the 100% renewable scenario. The lower bound on daily generation is higher. Reactors would run at near-constant levels like now, the only difference being that they'd recharge storage systems at low-demand times.

Or it could turn out that building very large storage systems, even capacious enough to e.g. ride through Germany's entire winter, is less expensive than building new reactors. I'm just trying to keep an open mind about a future role for new reactors. I'm pretty skeptical about starting new reactor builds right now. My strongest present opinion about power reactors is that it's a shame to close working units while their attached grids are still consuming fossil combustion power.