I don't think that a lot of people are saying that it can not be done. What I hear people saying is that it is a bad idea.
Sure, you can make a modular phone -that will be (de facto) technologically worse or more expensive than its non-modular counterpart. But does it make any sense to do that? The question is not how many variations of a phone we can have, the question should be how many variations of a phone we need. And I do not think that every customer needs its own variation or that it is worth developing for that one person who needs a phone with a weak processor and a super strong camera.
Sure, you can make a modular phone -that will be (de facto) technologically worse or more expensive than its non-modular counterpart. But does it make any sense to do that? The question is not how many variations of a phone we can have, the question should be how many variations of a phone we need. And I do not think that every customer needs its own variation or that it is worth developing for that one person who needs a phone with a weak processor and a super strong camera.