I once had a job mopping floors and was quite successful at it, even if I say so myself. Based on my experience, do you think it is reasonable for me to claim that I will eventually develop techniques for cleaning the oceans of all plastic waste? Folks are criticizing the pie in the sky claims, not that they can do anything at all.

Seems a bit of both. But no disparagement to your floor mopping (as I once was a dishwasher in a commercial kitchen myself), but there's a big gap between cleaning a floor, or a dish, and creating frontier models and spaceships.

That said: I think solar is niche, and a moon-shot for how they want it. Nuclear is the future of reliable energy for human civilization.

I think the K-scale is the wrong metric. I don't think we should be trying to take all the sun's energy as a goal (don't blot out the sun! don't hide it in a bushel!), or as a civilizational utiltiy - I'm sure better power supplies will come along.