I think I agree with the idea that it is better to turn the smartphone into the phone you want, but I think it might require a bit more work than just not installing TikTok :)

I doubt you'd see many ads in the iPhone Assistive Access mode, which can (sort of) turn an iPhone into a feature phone. You might also need to swap out a few Apple apps though. https://support.apple.com/en-sg/guide/assistive-access-iphon...

Because the iPhone has some ads for Apple services baked in, which is what the article is about. But it's really minor. The people complaining about this don't actually have iPhones, haha.