As a generally darker theme person, I'd probably choose this look most of the time anyway, but I suspect that my lighter theme-loving brethren and sistern will be looking forward to such time as we can lighten it up. Otherwise, I think it looks pretty spiffy, especially compared to what we had just 6 months ago:
FYI: as of 2021.09 EA build 099 these menus have been reverted to a black on light grey, though from what I see on my PC, the background grey is a darker that 2021.06 and the highlight color is darker.
Also, there is now a border around the fly-out menu when we expand a category. To me the border is a definite improvement because it makes seeing the expansion fly-out much easier.