The sensors themselves are generally standardized sizes, and the top end ones aren’t much (if any) larger. They may have slightly larger supporting hardware to allow better electrical insulation to reduce sensor noise, but not significantly larger per sensor.

To the best of my knowledge, the post processing on flagship phones don’t use multiple photos from different cameras, they use machine learning / AI, which can run on lower-end phones too, it just takes a bit longer. Which imo is totally fine because it’s done by the photo app, not by the camera itself. The only thing that I’m not sure about is the “portrait mode” which seems to do a better job if I select portrait mode in the camera rather than apply a portrait effect in the photo app, so maybe it’s using multiple sensors; but I’ve never seen a phone that had a better than 5% success rate at producing a portrait photo that wasn’t absolute garbage, so that’s a feature I’d be happy to sacrifice.

I don’t need all the processing power, I don’t need all the memory. I need a good OLED screen at a size I can fit into my hand, all day battery, a good amount of storage, and a top of the line camera sensor and lens.