You wouldn't be blocking all of the suns light. That'd kill us. Blocking 2% would be a noticeable "fix". It's been a thought out on paper project for decades. It's "possible" in the strictest sense, but would take something (or many smaller somethings) the size of most of South America to do. It would take thousands of launches to a destination around 800,000 miles away, and then it would also all have to be able to adjust for orbital changes because the lagrange point isn't a stable orbit.

We just need another massive once a millennium volcano eruption. Throw the world into chaos and starve half the population to death while the earth is half covered in atmospheric ash for a year. The slow Thanos snap.