Unfortunately, I think one of their problems is that iPhones last too long. I'm still very happy with my iPhone 6. The spec updates aren't as tantalizing as they used to be.
Having a reputation for low quality would kill the demand they have now. Their strategy is to entice upgrades, not to replace on breakage. Which is better, as it makes for a happier consumer that had choices on this.
BTW: did you change your battery?
But they couldnt do it forever