I disagree, what you can get in a inexpensive body these days is pretty crazy. Sony has been pushing the envelope pretty hard the past few years and been putting out some truly amazing cameras for unbelievable prices. The A6000 at $800 was crazy at the time, and the A7iii last year at $2000 definitely surprised Nikon and Canon with their mirrorless they were developing.
A full frame sensor can easily cost $600-$1000 without even considering anything else, yet these cameras are in the $2000 range and include highly sophisticated stabilization systems and professional video features (e.g. 4:2:0/4:2:2 output). Those are typical to low margins for a technology product.
Regarding your complaints. Realize that higher end cameras are meant to be a professional tool. Thus they tend to favor conservative reliability and interface continuity over anything else. The camera app crashing like it might on your Android phone is unacceptable on a camera, so they run more reliable and specialized code. Though speaking of Android, Sony cameras do run a modified version of Android, the previous few generations of cameras had somewhat of an app store, and people even got hacked APKs running on the camera to add missing functionality.
I do agree that camera manufacturers are purposely leaving out software features though. Stuff like an intervalometer and focus stacking should be standard on every camera. Plus, as you mention, some vendors are hobbling features to try to get users to buy more expensive cameras (like a 1.7x crop for 4K video on Canon, because they really want you to buy a C200 @ $7500).
To expand a bit more on interfaces, there is an interesting argument for and against it. It is no surprise that the camera industry is shrinking, and that the people most likely to buy new cameras are going to be those that already own an interchangeable lens camera. Thus manufacturers don't want to upset their customers by changing their interface too much. Companies like Hasselblad that produce more specialized luxury cameras have come up with more modern interfaces for their recent cameras. While I would personally love to see Canon/Nikon/Sony step up here and create a proper, modern touch interface for these cameras, they won't anytime soon. In everyday use, most of the interface with a camera is with physical controls, at most your common interactions with the software is changing options that are part of a quick menu.