I doubt that level by Hitch is about gameplay even 20 %...

Also, I'd like to point out that levels like semi and bblair have the best kind of flow you can find. Navigating the level is easy with a few jumps, but it is also something you can develop in.
It is but silly if a level doesn't require the player to jump. That's when you're converting the importance of skillful movement to luck with lag in terms of gameplay.
Gameplay in levels with overly good flow isn't about skill nearly as much as in levels like semi or bblair where you actually have to jump around and not run in a straight line. It also makes gameplay a whole lot more interesting.

Anyway, gameplay is the main course, complemented by the eyecandy.
In the end, it's a good idea to have a healthy mix of levels that focus on gameplay and levels that focus on eyecandy.