I think awareness of microplastics, etc. kind of undermines this theory. In the 60s we were spraying all kinds of crazy crap - CFCs, DDT - into the environment

I think awareness of microplastics, etc. kind of undermines this theory. In the 60s we were spraying all kinds of crazy crap - CFCs, DDT - into the environment and plastic was already pretty widely used, while recycling was nowhere in sight. 5-6 decades of additional plastic accumulation is not nothing, but people are much more aware - hence the return of metal water bottles, for example. Many pesticides/herbicides have also either been banned outright or are much harder to get since then. Plus microplastics likely accumulate over your lifetime - a mental health issue caused by microplastics would show up much more quickly in the elderly of middle aged than in teens.