Waste-to-energy is not your old, polluting incinerators. The technology has gotten amazingly good. They make the most sense when you can capture and use the heat as well as the energy (as in district heating.) Presumably Dubai doesn't need a lot of space heat but maybe they can use it for industrial processes.
Waste-to-energy is not without its critics. Some worry that societies will be forced to create waste to feed them. In Sweden, their recycling numbers still stayed very good despite the waste-to-energy option but they are now importing waste from other countries. In Sweden they also use the W2E plants to store wind energy at night when demand is lower.