Re: :looks at watch:
"I would expect any improvements in solar panel efficiency or turbine shape or whatnot could be phased in more-or-less with scheduled maintenance/renewal. "
There just isn't enough theoretical improvements left that will make wind and solar drop in replacements for baseline power generation. All of the storage options thus far are too expensive, complicated or dangerous (some are all of that).
The talk thus far in government circles has been on the best hammering techniques to pound the square peg into a round hole. Very little to no discussion has been entertained about finding the appropriate square hole. Cleanly produced energy is a good thing and is useful if it used according to the restrictions that come with it. If it can reduce the energy used by burning fossil fuels, all the better. The solar system I'm working on at home won't have me disconnecting from the grid but rather being used to power the most common usages I have such as running a freezer, an evaporative cooler and putting heat in the house on a winter day. The ROI to be totally off-grid won't pay back for me in the years I likely have left.
As Professor Bernardo De La Paz famously said "When confronted by a problem you don't understand, do the part you do understand and look at it again". Getting people to the moon was a goal, but there were a whole bunch of intermediate steps in getting there. It would have made no sense to have a program to go from zero rockets (discounting the Chinese gunpowder rockets) to walking on the moon in one go before doing something like Sputnik and then suborbital manned rockets followed by more increasing difficult missions to work out how to do all of the tasks the moon flights required.
What intermittent processes can we do with wind and solar? That can be looked at while at the same time we can be looking at improving nuclear power to make it more safe, less expensive and even more reliable. It's not one or the other, nor should it be.