This is extremely disingenious. A particular plant might have 90% availability, but collectively with a handful of plants hitting five-six nines should not be a problem. The crucial thing is that the performance of nuclear plants is uncorrelated: if one plant is not producing power, there are not many situations in which other plant aren't producing power either at the same time. On the other hand, with solar or wind, correlated performance is typical: winter tends to happen to the whole country at the same time, bad weather covers huge swaths of the country, etc. This might be worked around to some degree if your country is huge (like US), but if you're, say, Austria, your only option is nuclear or depending on the neighbors on the most crucial thing you need.
You say that a handful of nuclear plants can hit five nines of reliability. Sure, but then you must also consider a network of thousands of wind parks that can also hit five nines of reliability without breaking a sweat. Even assuming a high correlation in wind conditions.
You say that import is not an option because electricity is so critical. But then how come all the world's nuclear power is dependent on imports of uranium from Kazakhstan, Canada and Australia? Not to mention oil and food imports.
Is wind power the perfect energy source? No. Is it better than what we have? YES.
Modern offshore wind farms features huge wind turbines built dozens of kilometers out in the sea on spots chosen by computer simulations to have optimal wind conditions. They can reach up to 60% utilization meaning that 60% of the time they produce electricity at full capacity. https://www.fool.com/investing/2018/09/04/5-stats-about-offs... Of course that is still lower than nuclear's 90% so what you do is that you build many wind farms. Especially if augmented with hydro power they can be a just as reliable electricity source as nuclear power.