a few problems with that:

first, it likely ends up with them becoming somewhat of a social outcast. no, it's not like bullies are going to be shoving him against walls for having strict parents. but it will be more subtle stuff, like not knowing how to play certain games, or not being able to be in the loop for social events, that will add up over time

second, after they no longer are under your wing they are going to be exposed to screens. period. not teaching them how to self-control could cause them to become the technology equivalent of those kids with super strict religious parents who get to college and way overdo it on the drinking and partying.

third, most schools are pretty technology heavy, and are getting more so. good chance that they'll need screen time to do homework. this also applies to an increasingly tech-saturated job market: not giving them that exposure to technology might put them at a professional advantage.

the issue for you wasn't amount screen time. it was how you were using it. teaching your kids to use technology to educate themselves, pursue their passions, and grow as people will get much better results than a blanket ban.