As someone without children you don't understand that parents need to rest after couple years of constant taking care of children :)
I was the smartest about raising kids when I didn't have them yet :)
The only way to really keep your child away from screens is to keep them out of the house entirely. They are going to see your computer and your phone and want it. 4 year olds understand a lot about the world, so it's not like you can just pretend you don't have these awesome toys.