Now, back to intelligent discussion...and your points.
1. We do, in fact, lack for test subjects. Its unethical to expose certain adolescents and not others to stimuli that may prove to be harmful.
2. It's fairly impossible to control for other potentiating, negative side effects when considering "Internet use" and whether or not it actually "rewires the brain." As the author wrote, all experience "rewires" the brain in a certain sense. That's just another way of talking about learning (experience-dependent plasticity). It is far too early to tell whether adolescent brains, which are already particularly and uniquely susceptible to the development of pathology, are negatively impacted by certain kinds, amounts or frequencies of contact with digital media.
3. Whether something is "changed" neurologically is only ONE way of searching for negative sequelae of internet/digital media use. Think of it this way: in many cases with clinical depression, there are NO (that is zero) biological markers for the disorder. In some cases, you can find gray matter volume changes or changes in the nucleus accumbens or amygdalae during autopsies that do not show up in MRI scans during the person's lifetime...or perhaps the person never had an MRI. But we would never say that certain experiences don't cause or exacerbate this person's depression, just because we can't find any neurological markers. The same may be true (and is, true) regarding Internet use, the teenage brain, and negative impact.
Try to think beyond "neurological deficiency" as the be-all-end-all of whether or not there may be negative impacts of Internet/digital media use.
As to whether we have "no generational neurological epidemics" being reported...we most certainly do. Rates of ADHD diagnoses have risen 42% since 2006. Many consider this "of epidemic proportion." Rates of all kinds of mood disorders have also risen significantly during the same time period. Some even argue that the Internet/digital media cause ADHD. Of course, it doesn't...but it isn't true that we have no significant neurological epidemics. All mental health disorders and learning disabilities could (from a neurologist's perspective), be described as neurobiological in etiology.
Is the author saying everything you know about the teenage brain is wrong? (referring to the general public)...and even she doesn't know anything that isn't bullshit? I'm sure she isn't saying that or she's wasting a lot of time in graduate school or wherever she is studying right now. She's saying, I think, that most of the public discourse about adolescent brain development, from a neurobiological perspective, is mis- or mal-informed. To that, I'd heartily agree. She's wrong that everything out there is bullshit, though. There is a ton that is known about the adolescent brain. It's just mostly descriptive and conclusions are highly inferential. That's different than bullshit. Saying "this is how it is, and this is how it works," if those conclusions purport to offer final explanations...then it's bullshit. I just don't think this author wrote a very smart article. She did, however, attract trolls and get clicks...and that's what most articles of this type are all about.
In terms of your question, it just shows that the author is still a student and that this article isn't terribly scientific, although she is ostensibly arguing against 'our' understanding of the neurobiology of the teen brain.
Whether you or I love the internet, or we think it helped us or harmed us, or is harming us, or harms some teens, but not others, or "rewires" some teen brains for the worse (a specious concept to begin with) isn't the point. Mills could have saved you, me and everyone else the trouble by just writing:
"I'm a neuroscientist studying the adolescent brain and I just want to say that the public discourse about adolescent brain development is way ahead of our actual scientific findings and evidence."
There are complicated reasons why neuroscientists and non-neuroscientists alike are rushing to get the results, however tentative, into the public conversation. Some reasons are financial, and some are based in real, earnest efforts to shift research priorities towards the earlier pubertal period because these researchers sincerely believe that that's an understudied, underfunded, under treated, critical time in adolescent life. Check out Ron Dahl's work at Cal...he's the main proponent of this position, but there are plenty of others.
[mod edit: removed trollbait]