Nobody else needs a DSLR, so this is a complete non-problem.
How does this excuse having a terrible interface?
You only think it's terrible because you don't need what it does. If you did, then you would think it's a great interface, because it does what you need. This is how I can tell you don't need a DSLR. You need a simplified, Fisher-Price camera. Sometimes those are great, and I have one. When I am just taking snapshots, that's what I use, because it is simple and good and small and light. I don't use the DSLR at all unless I need something it's got that the super zoom doesn't, like RAW. It doesn't have any more lens.
Because I need to be able to change the setting quickly, and also while holding the camera with both hands.
So make the settings that need to be changed fast easy to change fast.
Yes, that's what they have done. You're just seeing settings you don't need to change and thinking about how inconvenient all those settings are for you, because you think the universe revolves around your balls.
There are a lot of features you could not possibly change faster than the time it takes to pull out a cell phone that given that they are buried in a menu somewhere.
You are completely incorrect. No camera has more than three or four levels of menus and I can navigate a menu structure like that much faster than I can get my phone out of my pocket. I may not have a spare hand at all, so the phone might not be an option at all. I can work my phone menus with one hand. I cannot work the phone and the camera at the same time with one hand.
Your solutions are dumb because they make the situation more complicated. All cameras will eventually have fancy-pants multitouch displays and then there will be absolutely no benefit whatsoever to phone interfaces. In the interim, that kind of functionality is of use only to a subset of users. If a brand did what you describe then the professionals would go elsewhere and the company would rapidly gain a reputation for making toys and then go away.