None of those studies establish a causal relationship. Correlation is not causation. Even the first study says "Longer time spent in cognitively stimulating activities (>1 hours per day) was associated with lower scores of both ADHD symptoms (0.96, 0.94–0.98) and behavior problems (0.89, 0.83–0.97). Time spent watching TV and engaging in physical activity were not associated with either outcomes."
I have a child with ADHD (age 9) and a child without (age 6). They are both highly intelligent, but compared to each other:
* My ADHD child is significantly more attracted to screens, video games, and quick stimulation in general. If he doesn't have a screen, he's much more likely to engage in simple, lower-focus activities like simply spinning and running in circles or just hitting things against each other. When given the choice, he will always choose screen stimulation.
* My non-ADHD child is more likely to play with clay and building materials, read, write, and draw. He likes TV and video games, but will very often decide to do other, lower-stimulation activities without being prompted. When outside, he explores and examines things, and will play more structured, imaginative games with rules.
* My ADHD child sleeps much less than the non-ADHD child. He has trouble falling asleep, and wakes up very early every morning on his own. It is impossible to "give them plenty of sleep" when they literally can not sleep.
* My ADHD child exercises much more than the non-ADHD child. He is more interested in going outside in general.
* My ADHD child does not like studying and can not focus on learning things. He learns less, he learns slower, he is disruptive in class. He acts more immaturely even when we take much time teaching him to behave like an adult. He is often depressed because he feels like there's something wrong with him because he has a significantly harder time just having fun doing things that other kids his age do. He feels depressed because he wants to learn things that he simply can not make himself sit long enough to focus on. He feels depressed because he knows he is being immature and disruptive and feels like he literally can not control it.
Given the same opportunities and treatment, my ADHD child has more screen time, more time exercising, less time sleeping, learns less, is less mature, and is more depressed. He is on medication now, but I felt the way you do for years, and it set him back severely in school and life, including his friendships and relationships with family. On medication, he is doing much better in every single respect, but he still struggles, and the medications become less effective over time (we're still trying to find something that works better long-term).
I'm going to be frank here. You are taking studies that show correlation, ignorantly assuming causation, and making judgements and giving advice about an area that you clearly do not have any personal connection to. ADHD may be overdiagnosed, it may have been underdiagnosed in the past (note that ADHD is strongly correlated with self-medication and addiction, which has always existed), but it's not something that you can really easily cause or prevent, and dealing with ADHD in a child is stressful and challenging for both the parent and the child. Assuming neglect among parents of children with ADHD is absolutely uncalled for, and contrary to my experience, where parents of children with ADHD are absolutely run ragged from years of trying to fight to keep their kids healthy, sane, and educated.