It's not a myth, you can make new items using recycled plastics. Of course, the recycled plastic doesn't have the same properties, but it doesn't mean that it can't be useful to reduce plastic production. Most plastic items do not require pristine materials anyway.

It's the same for paper and cardboard, and it's much better to reuse it as much as possible to avoid cutting a tree. Letting it rot releases the same amount of CO2 than burning it, by the way.

https://plasticsrecycling.org/how-recycling-works/the-plasti...

I'd argue it's kinda a myth, because I used to believe we could create a perfectly closed loop (you know, like the one the recycling symbol suggests) if only we could cleanly separate the materials (which in my imagination requires consumers to vigilantly separate the waste into dozens of different bins). I'm beginning to think I was wrong.