Professional photographers change their settings regularly. So do advanced hobbyists.
There are hundreds of settings on an SLR camera that even a pro photographer isn't going to touch routinely if ever. And there are settings they do use with some regularity that are hard to get at and/or difficult to customize. The fact that they've learned to use a crap interface with the greatest possible efficiency doesn't change the fact that it's still crap.
Nobody else needs a DSLR, so this is a complete non-problem.
How does this excuse having a terrible interface? Even if only pros used it a better interface benefits them most of all. Furthermore what you think non-pros "need" is irrelevant and arrogant. A well designed interface will work well for pros and hobbyists alike.
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. They've done some of this but they refuse to finish the job. Sometimes you do need to change things quickly, that is true. That doesn't describe a very substantial proportion of the menu options. Probably >80% rarely if ever get touched even by the pros.
I might need to change the setting faster than I can get my phone out of my pocket.
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. I'm not suggesting everything be offloaded but I think it's pretty safe to take something like the filename formatting out of the camera menu. You're not going to change that in a hurry. And frankly the argument that every feature of a camera needs to be in a menu just doesn't match reality. NOBODY needs every possible feature of the camera on the little screen. NOBODY is going to change a lot of those settings "quickly while holding the camera with both hands". Some they will. Most they will not.