Burying the compressed bricks is actually a great way to handle sequestration.
[1] https://www.npr.org/2020/09/11/897692090/how-big-oil-misled-...
A plastic paver walk way is nicer than a muddy path littered with plastic refuse.
For instance, the issue with flammability/melting and also microplastics contamination is real and worth asking. I wonder if using these bricks as building foundations or something might not be a good way of solving both problems at once. However, that's an idea that would only arise if we ask pressing questions in the first place.
From their perspective it is a good use of something that might otherwise be litter.
I've always wondered if they couldn't compress it, like those bricks but cubes, then use those cubes mixed with base fill dirt for building bridges and such. Like the massive earthworks they build around highways and such.
Now with the unknown prospect of increased weapons development over a century, it gets even less ridiculous. Imagine the international quagmire where something worse than nukes exists, but with a much easier manufacturing process.
In any case, my exact argument isn't that extinction is the most likely scenario. Just that the least likely is one where we are just chugging along with the same overall technological capabilities. Worrying about what will happen to micro-plastics in a hundred years is like a New Yorker worrying about the growing quantity of horse manure in the city circa 1894.
Delaying some of the carbon we put in the atmosphere for hundreds of years is massively useful, because it buys us time to try stave off and ameliorate some of the effects of climate change.