They're simply recapping various other studies, and attacking the messengers is pretty telling. In fact, every single one of the "studies" that you cited are meta analyses that simply take the already flawed data and outcomes of other observational studies, run them through magical Excel formulas, and then Dan Ariely the desired outcome. You're pretending there is a difference here that there isn't.
Regardless, from your very first meta study-
> It is possible that the weak inverse associations between dietary fibre or whole grain intake and risk of colorectal cancer could result from unmeasured or residual confounding by other dietary or lifestyle factors. Higher intakes of dietary fibre and whole grain are typically associated with other health behaviours, such as higher intakes of calcium and folate; higher levels of physical activity; lower prevalence of smoking, overweight, or obesity; and lower intakes of alcohol and red and processed meat.22 27 63 Many but not all of the studies adjusted for potential confounding factors, although not all potential confounders were adjusted for in every study. In analyses stratified by adjustment for confounding factors
This is junk nutrition science, and the field is rife with it (every week someone does this junk and you get another "super food XYZ protects against ABC"). A very weak correlation is found between a healthy practice and an outcome that tends to come from healthy living. Story at 11.
The funny thing is that I heavily lean towards fibre options, and ultimately have almost all ideal, healthy practices. Fibre is good for everyone. But the narrative around fibre and the rise in youth colon cancer is such a ridiculous non-starter, for virtually every reason, that it's just a gigantic distraction.