But It’s not complete bright. As you can see the start menu and the taskbar is dark. 
i have not touched that menu deeply, i just set to dark because i have photophobia
the left one is the default basically, i am using breeze, this on default leave me almost blind
the one in the middle is the one i use, always dark, all the time
the last one if i am understanding it correctly, changes from bright on the day to dark in the night, to help with tired eyes
now, you mention one set of colors, i am mentioning another, when you open system settings, there is a option on the left called quick settings, were i see what i described
now, if i go to colors and themes, i get a different menu, with both, first breeze, and under it the fedora you mention and show on that picture
alot of distros use a dark start menu and a dark taskbar, from what i have used, few are the ones that use the start button with a white color theme, and this over multiple desktop environments, not just kde
from what i remember only debian and suse use a white menu by default, so the light one uses windows with a clear color, the start menu with the taskbar are dark and in my opinion that makes it look very nice
