hidden dangers

I agree that too much technology isn't healthy. It leads people to be more sedentary.
I also find it difficult to believe that being surrounded by and in close proximity to radio and electromagnetic waves isn't harmful.
Unfortunately, there are a wide variety of suspected causes of many other things you mention, which are too many to go into here, but I will point out a few. Don't forget that there is tonnes of pollution in the skies.
Also, due to widespread travel, we are exposed to viruses and other germs at a much higher frequency than in the past.
I am a food allergy sufferer. So are many of my relatives. It goes back generations. I had friends who had had anaphylaxis, growing up in the 60s, including one who had an allergy to peanuts.
What has changed historically is the amount of exposure to allergens on a regular basis. Go to the store and look at the ingredients in cookies, crackers, soups and sauces. You will find soy, wheat, corn or corn syrup in almost everything. Look at chilled cookie dough. It will have these as well as several types of nuts and other things you would never imagine.
I have found cheeses to contain soy or other unusual products. Many cereals, candy and other items warn they may contain traces of nuts. Any exposure to trace amounts of an allergen can trigger an immune response that prepares for a severe response to subsequent exposures.
Other things that have changed with our food supply are the quality and types of substances added to food.
For example, the types of oils used. Butter was more widely used as an ingredient. Then hydrogenated and partially hydrogenated oils were popular, but turned out to be bad for health. Now palm oil and palm kernel oil are becoming popular and are unhealthy. Cottonseed oil, used for industrial purposes, is being used as edible oil. It is linked to lower sperm counts in men.
We have genetically modified (GM) foods, where let's say, a gene from a sea plant or some other organism is imbedded into the DNA of a plant to ward off pests, fungi, or resist drought.
Sounds reasonable, but why are food and chemical companies spending lots of money to prevent legislation requiring labelling of GM foods?
Something else that older folks will recognise that has changed with our food supply is its containment.
Prior to the 70s, I can't remember anything being sold in plastic containers. Everything was in glass, cans, or waxed boxes. Grocery bags were paper. Plastics has a lot of good points. It doesn't break easily and is much lighter, but some plastics can leach chemicals into food. Some of these chemicals affect hormones in humans.
People should be careful about what types of plastics they use for food storage.
Health awareness has increased awareness and diagnosis of some conditions, so comparing statistics of now and then might be misleading.
A lot of 'problem children' probably had attention deficit-hyperactivity disorder back then, but would never have been diagnosed. Who would have known if they had Type 2 diabetes or heart disease? Things like that used to be normal, and people didn't always know why someone died.
Don't you think artificial lighting has something to do with sleep disorders? Is it natural for most people to be up so late? Light affects one's biorhythms, which affect one's health.
It has only been a little more than a century that humans have been staying up so late on such a wide scale. Anyhow, think about it.