The issue is the degree of contamination. Different municipal waste streams all have their own internal systems a 98% plastic stream and a 99.9% plastic stream are very different economically.

Completely separate from that it’s a political issue as nobody wants their country to be thought of as a dumping ground. “Malaysia says up to 3,000 tonnes of rubbish will soon be returned to the UK, US, Japan, China, Canada, Australia, the Netherlands, Germany, Saudi Arabia, Singapore, Bangladesh, Norway and France.” what’s not mentioned is this represents 1% of plastic sent to the country. The don’t want to ban the process because the other 99% is quite valuable domestically.