I think the first thing is to prevent kids from watching too much TV. Enforcing strict laws at home for kids especially those who are younger than 18 is really a crucial thing for the home. Kids who spend too much time on the tele would develop an attention deficit and will usually have a hard time focusing on their studies in school.
Usually from what I see is that parents usually may be too busy and sometimes allow their kids to play with an electronic device of watch lots of tv is because it would take the work load of taking care of them. Kids who are on hooked on to electronic devices usually love the things they see on it.
If a kid is already addicted, it would be really difficult for the kid to disengage from watching excessive television. This is because it's like taking drugs, smoking and other addictions which there is a withdrawal syndrome. Kids feel like zombies, if for example they have given so much time to watch tv and all of the sudden their tv viewing time get's reduced and they would show some extreme anger issues. That's what I think may happen.
The firs thing to do is to occupy their time by bringing them outdoors more often to do more physical activities. Get them to go to join some outdoor activities and it may encourage them to reduce their screen time. The television afterall is always fixed at home. My friends has kids that learn everything from youtube which is really a bad example to learn and his son screams and I asked him, why let him watch so much of those tv. It is them I found out who empowers their kids on these activities.
Give them limits in watching TV like an hour a day. It actually works because my nephew is not indulged in watching TV as he was given an amount of time per day.
Encourage them to play outdoors. That way they will be active physically unlike most of the kids now who are holding their phones playing.
Spend some time with them like having an open communication. You can even have a time playing games like Jenga, UNO, Word Factory, Scrabble, and the likes. This way better than watching TV.
Provide alternatives. Spend time with them, go to museums if possible, go out for a walk, engage them in discussions about various topics, motivate them to be curious and follow a hobby, read books or play sports. The more possibilities they have to spend their time otherwise the less interested they will be in television.