Why don't we use awnings anymore (2022)

I think the builders of the past would be amazed by modern technology like argon filled double paned windows with advanced window films to reflect the heat instead of letting it in.

But yes, let's bring back the awnings too. Sometimes the low tech ways are easiest and best. I will say that I don't think awnings alone can save a stick built modern house from the heat. Part of the key to old houses staying cool was high thermal mass: lots of brick and stone that could stay cool during the day. As great as modern insulation is at keeping hot and cool separate, a modern insulated wall doesn't cool it's surroundings like a high thermal mass wall would.

Moving to a world where we combine passive cooling and high thermal mass construction with the benefits of modern tech will be key in my opinion.

What happens when they break?

You replace them.

I was referring to the cleanup of toxic materials and the safety aspect.

Argon is a largely non-reactive noble gas. What toxins?