My understanding is at odds with yours. Problems extend well beyond calorie density.
"Processing" covers a lot of things but is often performed for shelf-life reasons. Preservatives are introduced. Ingredients are cooked at very high temperatures to eliminate ambient storage issues. Processing also allows recipes to be precisely tweaked by committee, adding salt, artificial flavourings, and [often controversial] sweeteners. Colourants are dictated by marketing too.
Aside from probable direct chemical issues, these flavour- and sodium- hyperdense foods screw with our expectations from food. They're also digested too fast, exacerbating glycaemic swings, even illiciting a Pavlovian response.
Your "filler" ignores the cause of today's problems. The problems above are caused by a 70 year postwar food race. Capitalism. The way out isn't more of that, we need to recalibrate. Everyday food _should_ be boring, so that treats remain special. Reclaim a taste for the boiled veg our great grandparents had. Get away from this boomer-fuelled sugar fetish.