@YouTube premium doesn't understand consent. You tell it "no" and it asks you again and again and again and again and again and again and again and again and again and again and again and again and again... I. DON'T. WANT. YOUTUBE. PREMIUM.
Sorry to hear about this. Have you tried clearing your app's cache and data or reinstalling it/its updates? If you're still being asked to subscribe for YouTube Premium, feel free to send feedback about the experience with the steps here: https://yt.be/help/feedback