What you describe is a matter of willpower. I would bet one could modularize a modern iPhone to previous levels of repairability with only 10% to 20% more space. But Apple wants those repair dollars...
If by making use of your "willpower" other things fall out of your control, then is not just a matter of willpower.
By making it modular you are sacrificing size, there are no two ways around it. The discussion gets nowhere if people keep claiming the same exact product can be built if you just try hard enough.
No, look, 10-20% bigger is a real tradeoff. It's not about willpower, it's about what tradeoffs matter to you. Apple doesn't want their phones bigger. They very clearly care about how thin and light everything they make is. And I can mock it all I want to (I don't own a single Apple product, because I really don't share those values), but given that they are incredibly successful at what they do I don't think it's obvious that consumers don't care about these things. You can argue this preference all you want, but until you admit _it even exists_ you aren't going to be able to have a useful conversation on the matter.
