Not sure if you remember but a few decades ago the message was the opposite. Paper and cardboard packaging, grocery bags, etc. were environmentally damaging, plastic was seen as far friendlier (no trees cut down), and much more recyclable.
Plastics use less resources to produce, but pose a problem in that they will always stay plastic. Paper, cotton, etc use too much water and are often combined with plastic anyway to make them more durable, hygenic and increase shelf life of the packaging.
There's one issue with reusable grocery bags no one seems to want to mention. You have to wash them! More water, detergent or worse spray them with potentially carcinogenic anti-bacterials.