I have similar thoughts and am very divided over this, despite that businesses I'm involved in are suffering losses right now. What am I doing wrong? Is my product bad, mediocre, useless? After all, I'm thinking, if my product could generate profit when I could run cheap ads and have a pretty decent retention rates, then fundamentally, what's wrong with it?

> ... opt-in approaches. Mail catalogues, e-mail catalogues, yellow pages, catalog websites, trade shows, etc. - all kinds of services where it's the user who seeks out advertisements

There's a big problem with this. I don't know what I don't know. Even though I wouldn't voluntarily opt in for ads on my Facebook feed if I had the chance, but some ads are so good that I am sometimes even thankful when I see an interesting promoted product. That's only possible because Facebook knows too much about my interests already. But again, I'm not among those who'd voluntarily subscribe to yellow pages in any shape or form. My IDFA has been disabled since my first iPhone, I have the best paid ad blocker in my browser etc.

All in all, I doubt the industry can make a U-turn and go back to the opt-in model. More realistically we'll have a bipolar world with Apple on one end of the spectrum and the rest on the other.