Sure, a whitelist makes YouTube less useful to a teenager, but it's hardly "pointless". Even a few whitelisted educational videos and channels could have huge value. You can send videos and channels to your kids' whitelists straight from your phone as you come across them and build up a huge library over time. My kids have dozens of channels and thousands of videos to choose from now, and I add more frequently as I naturally come across them in my own causal browsing.