Give it a couple of years. As I mentioned elsewhere in the thread, mirrorless is already starting to displace mid- to mid-high-range DSLRs into the used market, and by then it should be displacing the high-end stuff too.
(And I feel you about the UI issues. Part of the reason I switched from a D5300 to a D500 was because the prosumer bodies are really designed to be shot in program auto, and you just don't have enough direct control of basic parameters - you need to be in the 7xxx range even to have an aperture dial! I'm waiting for D850s to start hitting the used market in numbers for precisely that reason - 45MP full-frame is just about ideal for the macro work I do, despite the relative DoF loss, and the UI commonality between that and the D500 means I won't have to worry about missing the perfect shot of a wasp or whatever because my hands got confused about how to operate the camera.)
(And I feel you about the UI issues. Part of the reason I switched from a D5300 to a D500 was because the prosumer bodies are really designed to be shot in program auto, and you just don't have enough direct control of basic parameters - you need to be in the 7xxx range even to have an aperture dial! I'm waiting for D850s to start hitting the used market in numbers for precisely that reason - 45MP full-frame is just about ideal for the macro work I do, despite the relative DoF loss, and the UI commonality between that and the D500 means I won't have to worry about missing the perfect shot of a wasp or whatever because my hands got confused about how to operate the camera.)