I'm not restricting my DS's screen time, as I would like them to be self-regulating by the time they leave for University and find their own equilibrium (guess who's been helping out with Chemistry homework this morning?!).
They're on it a lot. But so long as they get their school work done to a good (for them) standard, do their household chores without moaning, and get some exercise every day, then I think it's fair enough.
Like a pp said, DS1 tends to cycle through phases. Before lockdown I hadn't seen him play his PS4 for a while, but he was on it a lot at the start, now he's playing on the PC instead. He's big into YouTube too, and makes a video each week. To facitate this, I have just got him Adobe Creative Suite, and once he's learned how to use it I'm going to hire him for the summer holidays to help with my business, to make up for missing work experience week at school.
DS2 has a good set of friends, and given half the chance, he's out playing with them. He also likes baking and making clothes, but you can't spend all day every day on those so then it's back to the screen... Minecraft and Fortnite online with friends or god-awful YouTube videos.
There is such a big generation gap between us thanks to the Information Age. I admit I sometimes freak out about screen time, but I remind myself that it's their normal in a way that it will never be for us.