- your entry level mirrorless is ~$300 of camera HW vs ~$80 of camera HW on the phone (very very rough estimate of sensor+lens BOM)
- the mirrorless doesn't have any of the physical constraints of being tiny and fitting in a pocket, which directly impact image quality
iPhones cameras are really amazing given the constraints.
But, perhaps most importantly, along the lines of what others have noted: you know, my phone camera may not be as good, but I have zero complaints about the impromptu photos of my kid growing up that I could never have caught with anything else.
It’s a lot easier to pump out quality parts for less money when you order 10 million of them and potentially helped finance a factory to build them.