There are some points many of these articles neglect to cover. Most plastics photodegrade and do not biodegradable. I’ve seen some studies where the plastics do break down but they still retain the same mass and volume as when they first went into the landfill.
Then there is the other point that people just do not recycle as much as they should. Most third world countries that generate most of the plastic waste don’t even have recycling capabilities available.