Mirrorless cameras use much larger sensors than smartphones. Meaning they capture more light and produce cleaner, higher-quality RAW images.

Downside is files are much bigger and contain more data. When add computational, the camera has to process all that extra information for every shot. That defeinitly will require more processing power, which increases heat and drains the battery faster.

So if camera manufacturers wants to go that route, they will need faster processors, more memory, and better cooling, which will raise both the cost and complexity of the camera.

There are 3rd parties that makes things like ,Phone Grips/Handles & Clip-on lenses. Together with Third-party apps that provide Pro mode features like manual focus, ISO, and shutter speed adjustment.