I wouldn't say that nuclear is the best option, nor cleanest, nor safest. Like anything, it's all circumstantial. Sometimes it makes sense, sometimes other options are simply better.

From what I've seen, nuclear is the best for base load on a grid scale. Basically: the load that the grid continually has, is well served by nuclear. To my understanding, most nuclear generation is fairly slow to ramp up and down, compared to other technologies, so keeping it at a relatively steady level, with minor adjustments and changes through the day as required, is the best use case for it. It's stable and consistent, which is to say it doesn't vary based on external factors, like the weather, where solar/wind are heavily influenced by external factors.

It's entirely on a case by case basis.