Raw sensor size in cell phones has massively increased compared to years ago, and improvements in sensor technology (BSI, for instance) has improved performance

Raw sensor size in cell phones has massively increased compared to years ago, and improvements in sensor technology (BSI, for instance) has improved performance of sensors of similar size. These did not exist before. Obviously processing is getting more powerful, but I think you're discounting the improvements in the space. There's a few notable exceptions (e.g., Pixel phones used the same kinda crappy sensor for many generations), but largely people keep using the newer, better sensor on flagship devices.