I don't know. Maybe their processes are horrid but I think it's more to do with a genuinely bad design philosophy and direction. Car interiors take a long time to develop and while I suppose Tesla could crank out the Model 3's interior from design to implementation in six months or whatever, surely Rivian and Lucid have more realistic design and production timelines especially considering they did not have massive established studios like Mercedes. And yet the products they offer are industry-leading. It's not really about the physical controls at all because Mercedes is attempting to create the same thing as Tesla, Rivian, and Lucid...they're just bad at it. Embarrassingly so.
If
@GranTurNismo's recent post is real - honestly I'm not sure, that dashboard looks photoshopped by a child - then it's further evidence that Mercedes is just completely lost and has no idea what they're doing. Even Honda got it right with the E, that tiny car's interior is beautiful with excellent usability, materials, classic design, effective buttons and ergonomics, etc, and it's not a blatant copy of Tesla like the Mach E and others.
I really do believe that Mercedes is just lost.
Edit: Speaking of Honda, apparently their 2024 EV CUV concept for Europe also has a Mach E style center screen which is not nearly as attractive as the E.
Edit 2: Also why the hell is Mercedes lighting up the interiors in crazy colors like it's a damn Holiday Inn? Everybody with taste knows not to stay in a hotel that relies on colored lights to get attention.