I think that we haven’t reached the insulation to weight ratio of down feathers, so that’d be another example where artificial fabrics haven’t reach some qualities of natural materials.

Yeah but it goes the other way round, too. Gore-Tex laminated textile jackets are amazing. Suppose you ride through rain, and it clears up 15 minutes before your destination, you arrive with a dry jacket. Leather just soaks it up.

I'd doubt feathers would be better insulators than aerogel.