The Gnome desk in 19.04 is objectively less beautiful than in 18.04 because there is no transparency.
I ask the developers to restore transparency on the menu bar as well as on the dock as on 18.04.
If you really want black by default then add an option to enable transparency at once
Noted that the transparency of the dock must be in correlation with the transparency of the gnome taskbar (as on 18.04 : https://doc.ubuntu-fr.org/lib/exe/fetch.php?tok=641400&media=http%3A%2F%2Fpix.toile-libre.org%2Fupload%2Foriginal%2F1524966552.png )