Nostr doesn't necessarily solve the "if you're not paying for the product, you are the product" problem. You can still pay and be the product at the same time. In fact anyone can collect your data if you use the same account between applications and what you "share" in public is inherently can be harnessed.

Why don't the nostr clients have sophisticated notification system that pushes the content to you directly when even the client is closed? Like you can subscribe to the accounts, hashtags or even "algorithms" and you'll see them on your phone notifications and you probably click them. All social apps have this and it obviously works.