> just adding metal to a structure is commonly not a way to solve the problem you stated, it just makes the structure heavier which means other systems have more to support
As a mechanical engineer, that is exactly how you solve that problem.
> point is that it isnt exponential/fundamental progress
You just stuck the goalpost on a rocket and shot it into space. You'd be hard pressed to show evidence that progress in this field was ever exponential - in most fields it never was. Logarithmic progress is typical; you make a lot of progress early on picking the low hanging fruit figuring out the basics, and as the problems get harder and the theory better understood it takes more effort to make improvements, but fundamentally improvements continue.
Incremental progress from increasing scale is, again, perfectly cromulent. It's how we've made advanced computers that can fit in your pocket, it's how clothing became so cheap it's practically disposable, it's how you can fly across the country for less than the price of a nice dinner. Imagine looking at photolithography, textile manufacturing, or aircraft 5 years after they reached their modern forms and saying "this has plateaued".
