Dr Mew doesn't claim that orthodontics don't work, he points out they are expensive and lucrative, and he claims that if we maintain a "jaw healthy" diet from childhood, orthodontic problems will be much less prevalent in the population (this is a related but independent claim from the "mewing" regimen) He says that the evidence is found by comparing modern jaws/bites with historical skulls which show there has been a dramatic "20th century" emergence of orthodontic problems which would indicate a developmental issue rather than a genetic one.

I don't know if he is correct or not, but it's a claim that can be independently measured/verified. Instead of using and publishing such sound science, the orthodontia community is using "cancellation" against him which certainly matches the lucrative aspect, though doesn't provide direct evidence.