I don't know if cancers and immune disorders are increasing. It may be that there is a greater awareness of these diseases. People would get sick and die from cancers and immune disorders but they were not recognized. So many illnesses, diseases and conditions were not understood or identified until the 20th century - particularly the later half of the 20th century. With the advent of global media and the internet awareness has grown exponentially.
My Grandmother was blind from the time Dad was 5 years old. She had Glaucoma. Doctors new it was a narrowing of peripheral vision but could do nothing about it. Mother's Grandfather lost his sight to cataracts Doctors knew it was from a build up behind the cornea but had no clue how to fix it. I have cataracts and will have surgery within a year. Easy Peasy.
In my humble opinion the apparent increase in disease it is more about awareness. My Aunt's first husband had a congenital heart defect. He died at a young age on the operating table. Today that same defect would be identified at or even before birth and corrected in infancy.