> In hindsight it probably would've been worth having a stepping stone between Hubble and JWST that proved some of these technologies in a cheaper and less risky way, probably with a smaller mirror. But here we are.

That doesn't really seem to be in NASAs DNA, to do smaller incremental improvements. Instead, they really upgrade big, in chunks with long time in-between. I don't know why they do it, but in their webcasts it been mentioned a couple of times related to James Webb.