That's hardly enshitification, the USB camera monitor feature is NOT USB video output capability, which remains as a hardware feature on all Xperia phones, it is a proprietary software feature for receiving video output from Sony's Alpha Cameras into the phone via standard USB-C port, and displaying the camera's viewfinder feed on the phone. This is exactly the same as what you can do with for example Spacedeck to use your phone or any other Android device as an external monitor for PC, but with Sony's own proprietary implementation. And Sony's implementation is exclusive to their professional Alpha series cameras, you could never use your phone as an external monitor of any other device with that feature, which would always require another software to encode the video feed to transmit theough the standard USB-C interface anyway. So it's been an extremely niche proprietary feature only used by a very small group of people who happen to be professional photographers, doing certain specific types of photography, and happen to be using certain Sony Alpha cameras instead of professional cameras from other vendors. I agree it's a ridiculous and beyond stupid decision from Sony but I do also think it's a bit of a stretch to call that enshitification, especially compares to the kind of practices from many other much bigger OEMs that have unfortunately become almost ubiquitous these days throughout an entire industry.

While at the same time, Sony Xperia phones remains some of the very few high end Android phones these days that still have BOTH 3.5mm headphones jack and SD card support, together with an open device policy where you're always free to unlock bootloader and root without artificially losing major core OS features.