Again, the issue is cost, and externalities. On the one hand the cost of nuclear electricity is low, but the externalities are extremely high. Time, public opinion, and long-term liability are all against it (and that's assuming it goes as planned.)
Sure, optimal storage has yet to be figured out. Batteries and pumped-water-schemes are working in some cases, but are not necessarily grid-scalable [1]. But work in this area has potential, and we've not reached any maxima here yet.
Technologies like compressed air, hydrogen and so on are sll in their infancy.
I should note that I am pro-nuclear. It's a lot cleaner than coal or gas. I'm just not sure it'll ever be economically attractive.
[1] on a household level, batteries that can store over-night amounts of power exist, send are easily available. This provides a cap on how expensive night electricity can be.