I agree that it’s a problem but it’s largely self-inflicted — you can just turn of the screen and go outside at any time.

It may sound strange but it’s that easy

Yes, but as a general attitude, this is unrealistic, like ignoring the effects of drugs because they are voluntary. All these things (food, substances, sex, social media, etc) exist on an invisible spectrum of willpower vs circumstances for each individual. In practice, there's some subjective line in that spectrum across which society can't afford to just say "it's your fault, so I don't care" (though wealthy/isolated people can!).