I think your points are certainly common ones, but unfortunately they rely on three major misunderstandings.
The first is that all the "cool shit" we built in the first half of the century was the low-hanging fruit of new scientific understandings and materials.
It's not that we were smarter, it's nothing to do with toxicity, it's just that we exhausted most of what you can easily do with nuclear, steel, engines, etc.
The second misunderstanding is that we're not still building amazing things. Being able to access Wikipedia or Google through speech recognition, or talk to anyone in the world from a cheap videophone in your pocket, is astonishing.
And the third is that flying cars somehow respresent the future. But flying car enthusiasts only focus on the "cool" aspect of it, rather than nuts-and-bolts issues like how they could be fuel efficient, how an average driver will avoid fatal crashes, if we really want urban skies filled with visual, noise and emissions pollution, etc. Flying cars exist. But they don't make any economic or practical sense to use.
If you think we're still not accomplishing astonishing things today, you're not paying attention. Did you notice, for example, how multiple companies put together COVID vaccines in record time? How is that not amazing?