That's one of these broad "sounds good, but isn't logical" statements.
We don't need "every clean" tech. If we have tech a and tech b and tech a is cheaper and can be scaled up faster, while tech b has a lot of challenges and is clearly more expensive in every situation then we don't need tech b. And I think there's a lot of evidence that in most situations nuclear (particularly new nuclear) is tech b.
If we have tech a and tech b and tech a is cheaper and can be scaled up faster, while tech b has a lot of challenges and is clearly more expensive in every situation then we don't need tech b.
The only problem with that is that theoretical "tech a" doesn't exist. Every energy production technology has some drawback or trade off. Nuclear is expensive, wind and solar don't work all the time, tidal is limited to coast lines, fossil fuel burning makes the climate worse, and so on. In the real world we can't limit ourselves to one single perfect solution.
