I don't think they are going backward, but they yet have to figure out how to make hexes work with a spherical map... C4 is the closest we got to have a full spherical world, but since Civ moved away from square tiles, it is now much more difficult to make it happen... but it is possible!
Also worldbuilder in C6 is very buggy, and underdeveloped, but compared to HK worldbuilder it's a miracle we have it works without need an actual debugger...
C7 is still wandering between new world map generation limitation restraints, so it will take a long time till we'll see a worldbuilder ...
A spherical map would be cool but has always been an elusive dream.