"Solar and wind power are not sufficient for spacecraft"

I guess you're right that solar is useful for 99% of spacecraft -- in that they use it currently. Not a very useful observation

"and many other applications"

Power in polar regions. How well does Solar work in Antarctica? Or Alaska for that matter?

It works super-great, collected in the tropics and shipped in chemical form. Before you object to depending on imported liquid fuel, consider that most of the world does already.

The main difference is that literally anybody can make it, not just "oil exporting countries" and "fuel refiners". And, will. And export excess production when local tankage is full.

Last I looked, round-tripping solar via liquid fuel and back to electricity was under 2% before transport costs

Maybe look again without assuming hydrocarbon. Ammonia is a good transport medium, liquid at room temperature under low compression.