Theres's nothing complex at visiting a repair shop to swap your battery. It's a full blown industry of OEMs and small shops.
It's something you would do probably every 2 to 6 years, depending on your budged.
I don't see the reason to pretend that there are hundreds of millions of a year old iPhones in the trash. The reality is that iPhones are very long lasting devices with very strong second hand market and strong repair market, even the broken ones are recycled for their parts.
Of course there is a strong second hand market, the iphone cost too much for a lot of people to buy it new.
I notice that you ignore every single arguments that you dislike. You admit yourself that replacing the battery is too hard for a regular person and must pay a repair shop to do it.
Repairing something, is, most of the time, swapping the defective part with a functional one.
Most of the people buy a new iPhone, or will ask yo Apple a battery replacement, most of the time, they don't ask to a repair shop.
"Better environmental outcome" you dismiss that, people will buy another iPhone due to this complexity, and this iPhone won't be disposed properly.
Also, the repairs shop are currently fighting apple for the right to repair.