That would be fine if consumers didn’t constantly want thinner, lighter, sexier devices that are waterproof. And before you say they don’t - they totally do.
One of the big reasons people buy Apple devices is their longevity. Apple knows this. Planned obsolence is a quick way for them to start loosing money. All these issues are the consequence of the market, a comprise they make while trying to compete with other, similar companies, with Pixels and Galaxies, not some malicious plan to get you to upgrade. In fact, people are more likely to upgrade if they are happy with their previous phone. If that phone runs like crap, you probably wouldn’t be willing to pay a lot of money for the next one.
Personally, sure, I would love to be able to replace the battery myself, but this iPhone would probably have a design that most people here would call boring, me included. We pressure all these companies to bring us tiny bezels and incredible performance and amazing cameras but we also hate creaky, plastic devices that can be opened or repaired easily.