I have bikes with R6800 and R8000. I can detect no difference in shift quality; they both shift great. Shifts are precise, repeatable, reliable. Same feel at the lever. Hat's off to Shimano: 11-speed Ultegra works great.

Why Shimano went to the lower-profile Shadow design? Who knows, it's not as if road riders are regularly laying their bikes down like MTB riders, or getting exposed cable housing snagged by roots and branches.

Probably just part of the broader trend that most new road riders come from a MTB background, so there is less sales 'friction' if the customer sees (sub-optimal) MTB-like features on their road bikes. Such as sloping top tubes, tubeless, hookless, suspension, fat tires, 1x, and pie-plate sized cassettes. On road bikes, these are all performance drains, but hell: makes for an easier sale.