Most computational photography inherently breaks giving the photographer direct manual control over how a picture is taken (shutter speed, aperture, ISO).
For example, HDR or low light staking means taking multiple photos. This requires a fast shutter speed to minimise change in the scene or subject. However, photographers sometimes intentionally want a slower shutter speed for motion blur, or to shoot at lower ISO for less noise and more resolution.
Actions like noise reduction, upscaling, etc are post-processing actions. They are best done on a large, high-resolution, color-calibrated screen; instead of a portable device with a small battery where you want to maximise the number of shots you can take before swapping or recharging batteries.
Bear in mind that modern cameras easily shoot in 40, 60+ MP. To truly perform noise reduction, or upscaling on those images require a lot more processing power, even with fixed-function hardware. Your "48MP" quad-bayer smartphone is generally processing a "pixel-binned" 12MP image straight out of the sensor, that might be resampled to 24MP (iOS) after post-processing; but was never anything more than 12MP. The hardware was never more than 12MP, except they sub-divided each bayer pixel into 4 quad (or 12 for some Samsung chips) to claim 4x/12x the spec sheet w/o real world benefits.
Your smartphone's SoC, is usually manufactured on the latest, bleeding edge 3nm or 4nm processes. They are also the most expensive; made practical because tens of millions of each chip are shipped each year. There are ~1m dedicated cameras shipped each year; from many different manufactures using different chips; usually built on N16, N12, or N7 for the bleeding edge ones.
No, they cannot just use a smartphone SoC. Smartphone image signal processors simply can't process 61MP at 20FPS or 30FPS or whatever the burst rate sports photographers demand.
Your smartphone uses an electronic shutter. Your proper camera probably has a mechanical shutter, which is generally superior but also requires more force to move.
The battery in your smartphone is probably ~2x bigger than a professional mirrorless or DSLR. Pro photographers buy cameras, in a significant part based on how many shots they can take.
> the GUI feels like something built by engineers rather than for end-users.
Think of the GUI as being built for professional photographers who's been using an UI for the past 20 years of their livelihood. You would probably be really upset if your OS decided to change established keyboard shortcuts like Ctrl+C or Ctrl+V. You probably wouldn't choose that OS, and if professional photographers won't buy a camera because the UI is "weird to them", you've wasted your R&D costs because the dedicated camera market for the past decade is essentially only professionals; with some amateurs and hobbyists.