No, burning it is not "rational", it is the very opposite. We talk so much of carbon sequestration, and then "rationally" try to release all of the already-sequestered carbon back in the atmosphere.
Not burning the plastic risks its turning into microplastics, which will tend to interfere with the physiology of all plants and animals.
There's a lot of talk generally of running carbon sequestration technologies and how important that will be. Burying plastic waste is exactly doing that, without spending the extra power to actually extract the carbon from the air.
The plastic in our bodies is not generally getting there from environmental pollution, it's getting there from us using plastic to wrap and cook the majority of our food and drink and cosmetics etc.