I suppose it depends on what the screen time is. DS2 is 13, he will eat breakfast watching YouTube which is usually something to do with physics (minute physics, physics girl, veritasium, V source) so why would I stop that?
Gaming is done with friends as a team, it can be Minecraft or Kerbal Space Program (build/launch spacecraft using physics) or where they are a SWAT team. It is their social interaction rather than hanging around on the local park. They speak to their friends on headsets and both my children have gaming computers downstairs so are not closeted away in their rooms.
My children's grades are high, their effort grades outstanding, but like RedSky they also do other things. Ds1 is 16 and both he and Ds2 do a sporting activity twice a week in the evenings, we swim as a family every week, we eat dinner together and spend time watching TV , listening to podcasts or playing co-op board games/cards mainly poker as they like the gambling aspect. Ds2 is in an after school club too. They read every night before bed, so it is about balance.
They don't have games on their phones and don't even move them around the house with them, why watch a teeny screen when they can be on a bigger one 
If they ever moaned about coming off games they know that they get a ban. We can turn off the wifi for individual devices so they know that we can and will do that.