It really isn't. For reference, across Europe we're currently having a meteorological phenomenon with bad weather, clouds, little wind, and low temperatures. It has been ongoing since ~october and is projected to continue into the winter. When Texas was hit with terrible weather last year, it lasted a few days. Multi-day storms, which take out solar and wind, aren't unheard of. 3 hours of storage is OK to even out things, but isn't nowhere near close enough to guarantee reliable electricity.
Personally I think small mass manufacturable fission reactors are the best bet but why are we hung up on either/or? We should aggressively pursue both nuclear and solar/wind generation.
Millions of lives are at stake.
I agree that we should invest in both. But it is not as easy as waving a magic wand. Energy project development is a complicated dance between local power market regulators, local and federal incentives, private investors, and shovel ready/cost-effective technology. And in the rare occasions when congress opens up the wallet, it is a small pie that everyone is fighting over, so the lobbyists start slinging arrows.
The fact is, nuclear can and will be a really great addition to the energy mix. But there are models out there that show that we can build a carbon free grid without it. The big question mark is on the future cost of storage. The consensus is that those costs are going to come down considerably. If so, then going all in on renewables likely gets us to a carbon free grid faster. But this is also a very US centric take. For example China likely has much easier road to rolling out nuclear (less regulatory hurdles, less local interference/input). Where as in the US, I am sure we can build a big national pro-nuclear movement, but the second someone proposes a real life project, the NIMBY's will come out of the woodwork.
This is not the current hurdle when it comes to more nuclear in the US or Europe. Nuclear is very welcome where it is currently under construction, and there's no regulatory reason that these sites have all become construction disasters, it's just bad execution of the reactors.
Even China's attempts to build the French EPR design took twice as long to build as they had estimated initially, and we don't really know how much more in cost.
Nuclear's path to new reactors begins with being able to build on a reliable schedule without exorbitant cost. There are many sites that would welcome more nuclear that would not have NIMBY problems, there's just no one willing to bear all the risk of finding that unicorn contractor that can actually build.
This same problem was also evident during the late 1970s and early 1980s nuclear projects. There was NIMBYism back then affecting projects, but there was also lots of construction malpractice that resulted in big cost overruns. US utilities can not bear the construction risk of a $10B project. Few entities can.
Even the much vaunted France doesn't have 80% nuclear on their grid.
Plus, energy storage production capacity is growing at an exponential rate. It's doubtful that we could grow our nuclear construction crews at that pace.
It's going to be very hard to nuclear to scale as fast as renewables and storage are, if there's even an economic case to be made for nuclear construction, and somebody finally solves the logistic problems of large construction projects in the modern Western world.
We know we can build storage and renewables, but we don't know how to build nuclear anymore, and none, absolutely none, of the nuclear proponents have any proposals to fix it. The best is an entirely new type of small reactor that has been rejects in the past because of its high per unit cost. Perhaps it will work, but who knows? It's a big risk, whereas storage and renewables are a sure bet.