I think it's not that simple tbh.
My three kids have phones, 16, 13 and 10. They also have really healthy social lives, do activities which keep them fit and use phones for loads of things, not just tiktok (although tiktok too). I am of the opinion that they get enough of the essentials that if they have a few hours switching their brain off in front of a device now and again then I'm okay with it.
One child does 12 hours activities per week, one does 10, my eldest does 7 plus an extra GCSE outside school hours. By the time they eat, wash, do homework and get to bed there's not a load of time in between for screens. I don't have to limit them by saying no, it's a carrot not a stick. All of them prefer to do other things almost all the time.
I think that the key is balance. Down time is important, but so is good old fashioned social activity. I think screens are mostly bad not in themselves, but as a symptom of a society where there isn't enough time in the day to get everything done without these tools which people come to rely on.