but half the battery life in video decode means charging your phone twice as often even if you don't watch Youtube all day

Most of the power goes into the screen. The Pixel 8 has a ridiculously power efficient screen. I have one. It also costs $300 to replace. The Fairphone's is $100.

other phones have sliders or slots that will let you live swap either card without even taking the back off

Slots and sliders inevitably weaken the phone frame making it easier to break. They also cost more to machine.

even the fairest phone is environmentally costlier than rescuing an old second hand phone.

Replacing a battery to rescue a Pixel will run you $100-200.

Many design choices make a lot of sense when looked through the repairability, durability and cost of repairability lenses.