Which part is false? "any kind of incineration" could be a broad definition, and I should have specified "any kind of incineration process compliant with modern regulation" maybe. I do not know about regulations in the US, but in EU they are pretty strict, thus incineration of non-inhert waste should be done (look for "Waste prevention and management" on the European Commission website)

EU waste legislation is based on false premises, according to your comment. There have been plenty of disasters related to landfill disposal. Complexity is also there, as a lot of chemistry happens and toxic subproducts can be generated, even if the waste is not toxic in the first place, just because of interactions with the ground. The sheets used to cover the ground are easy to scratch, costly to replace, and accidental damage is often ignored. Monitoring lasts for decades or more, with greenhouse emissions. The stability of the terrain under and over landfill could also change, as there are processes that run for a long time.

I would highly suggest attending a university course on waste management if your country allows you to do that for free and without registration.