what does "modern malady due to the demands of 21st century life" even mean,
Yes, it's vague. One of the demands of 20th and 21st century life has been coping with an unrelenting onslaught of toxic exposures.
Some of those remain to be identified. Another stressor is the proliferation and evolution of a long list of specific viruses.
Some of those remain to be identified as well, especially because they mutate quickly into new forms. (And are helped along by bioweapons labs in some cases -- one of them is in Sierra Leone.)
When people mention "stress" in connection with CFS, it's usually what
@A.B. is talking about. That is not a claim that can be substantiated, since it's too hard to measure. Physical stressors are somewhat easier to measure, and many of us here know what triggered our CFS.
If the interview questions are well designed,
@Alexbickler` could really do some great research. I can't think of a more qualified and educated population for him/her to interview than the one here on PR. Alex, why don't you talk to some of the senior members so they can offer suggestions, once they find out where you're headed with this dissertation?