Go on, give us some numbers.
Because 7Bn people multiplied by a few kg/year doesn't seem trivial to me, but sounds like you can prove it.
7 billion kg at the density of water would fit in a cube 200 m on each side.
All the plastic ever produced could be stuffed back into one medium size coal mine. There are thousands of such mines and they are already ecologically disruptive.
It's a large amount when you think about the logistics to move it around the world, but a small amount compared to the total amount of stuff we take out of the earth.
The main thing about plastic is that it’s made from oil, and oil already exists in the ground. Putting it back into the ground is basically neutral minus the pollution involved in manufacturing.