The tiny sensors are a marvel of technology but have absurd levels of noise though. They're essentially unusable as traditional single-shot readout sensors in anything but exceptional light conditions. Internally phones take multiple shots and do an enormous amount of postprocessing for each shot. It's a completely different technique.

You can get a feel by how much post-processing is done by installing something like "opencamera" on a flagship phone, disable all filters and look at the raw file (if your phone allows it) and compare the results.