This is from 2017. If this was a viable system, I would suspect it would be mor3 widely used by now.
It has been tried before. There were many issues with it, starting with the fact that not all plastic waste is the same and failure to correctly sort out the plastic correctly results in the reaction being poisoned with the output being unusable. For it to work, consumers or other feedstock producers would literally have to be able to sort the different plastic types 100% correctly, something that doesn’t usually happen.
Oil has been cheap since 2017. Economics drive moves into new technologies in mature markets, not 'it exists'.