It is easier to process a single type trash. Home trash is where burning get pretty expensive because people put all sort of stuffs in there. And I am sure the energy is net negative to.
The main issue of trash has always been separation.
Which also iirc Japan does very well. Sure, the power generated is connected to it's grid and it pales in comparison to their other forms of energy production but it is also a part of their waste management policy.
The main issue of trash has always been separation.