Nuclear is so ridiculously energy dense that there’s no near future where we’re in danger of running out of it and nuclear hopefully soon won’t even need to rely on fissile materials, since we keep getting g closer and closer to getting fusion working.

And solar and wind and hydroelectric and other renewable are also great but they’re variable. Sun only shines locally for so many hours per day, wind doesn’t always come from the same directions or speeds, hydro is quite climate dependent, relying enough water to refill reservoirs.

I’m not saying we shouldn’t be also building up renewables but every powersource has its limitations and making a mix of all of these to cover each of the downsides is our best bet.