Except it's not that simple. How do you get parents to accept their responsibility to change their behaviour for the sake of their kids
I find it very simple - Mini D has an hour on her iPad, max, and that's only after homework. Then for every hour on the iPad she has to spend an hour reading a book. I walk her to school. I ensure she plays physical games, and she's a champion cheerleader as a result (my eldest was a martial artist with 3 black belts in different disciplines, second a cross country runner, third a kick boxer). I feed her sensible food with of vegetables, and the occasional sweet treats don't come unless shes eaten her veggies first (her favourite sweet treat is actually raw carrot, which she often chooses over chocolate). Complaining, tantrums and whining dont work with me - i don't let the tail wag the dog. Start down that route even just once or twice, and you may as well not bother trying. Kids are master manipulators so you need to stand firm.
This is mind bending easy stuff, managed perfectly well by parents across the world, and the only reason not to indulge in thoughtful, balanced parenting is laziness. Easy, easy, easy. Anyone who can't figure this out probably doesn't have sufficient iq to know how to breathe. Christ, I've never had any lessons on the subject but I figured it out.
As for making parents take responsibility - that's easy. Carrot doesn't work, the biggest carrot being the physical and emotional welfare of their children. In that case it's time to wield stick - your kid is a persistent bloater and their health is suffering, have a fine. You've been seen driving your kid to school every day this week yet live only 3 streets away - have a fine. Your kid's not done his homework again yet but has found the time to be on his X station every night - have a fine...we need a series of adverse consequences for parents whose adverse behaviour is affecting their children's development. Of course, it will absolutely never happen - no government has the political will, and too many bleeding hearts will whine about having to suddenly take some responsibility for their parenting for a change.
It will absolutely, never, ever happen - but the solution is easy. It's the will to do so that is lacking.