For instance, how do you change the key repeat delay in the modern UI? I have looked and I actually can't find a way to change it. I have to use control panel.
Just looking at the modern UI is an eyesore, there is so much empty space, a menu that should be a 600x400 rectangle takes up the entire screen. The information density is comically low. I have to scroll up and down this giant monitor sized list to find the one thing I am looking for. It's horrendous.
Settings is a slow, bloated mess, as you stated elsewhere missing many settings, and was in general designed by schizophrenics.
A primary reason for the sorry state of software today is the absolutely delusional priority that software should be "pretty" vs it being functional.
Send all the UI/UX wizards packing, give them a Starbucks apron where IMO they belong, and watch software usability and customer satisfaction improve over the next 5 years.