When it comes to spending time watching TV or playing video games or even binge watching Netflix, there is no direct toxic effect on children. And so, it isn't bad to reward your children with a little screen entertainment once they're done with their homework. Although, it is more important to know what is displacing. You should first analyse if everyone's screen time is under control. You also need to as yourself if it is interfering with any other social interactions or activities that you might want to do as a family. If it is so, then you need to reduce your screen time.
Make a plan and stick to it so that everyone understands when and how much they are allowed to use the screen time. This is very important for the adults in the home too so that they can stick to the boundaries. For example, if you as a family decide that you don't have screens and instead spend a good time at the dining table, all of you need to abide by that.
It's all about prioritizing the face-to-face interactions, very importantly before the children go to sleep as it can make the bedtime much easier and relaxed. If the child displays defiant behaviour around screens like refusing to stop watching and joining for dinner only points out to a wider parenting issue when it comes to applying boundaries.