I order a new battery online.
I remove the backplate of my phone.
I swap the old battery with the new one.
For my new phone, it's exactly the same, but in need to remove 6 screws.
No need for steady hands, without screws, my grandma could do it.
Also, what you describe is not about repairability, thats replaceability.
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.
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.
Sadly they can't replace the battery without the iPhone showing 'not genuine apple battery'. https://www.youtube.com/watch?v=NwRYcEI-wx8 Apple admit themself that their iPhone are made to last 3 years : https://www.mirror.co.uk/tech/apple-reveals-iphone-lifespan-...
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.
Or maybe expected product usage is not the same as building not to last beyond that but you want to interpret it like that despite the evidence.
You should quit watching the repairs shop guy, he is not the most godd faith persons as he built career on bitching about Apple.
Back in the days I replaced my iPhone 4s battery myself but it's not worth my time now days. Nothing complicated, you just need steady hands and sharp eyes but it's better done in the shop because they would have tools to hold it still and they are used to do it - so less chance to screw up. The replacement batteries often come with the special screwdriver that some people pretend to be impossible to get. In case you don't have the screwdriver a pointy knife would do too.