Did anyone miss the removed feature? If not, maybe it's not really a regression. If they did ("My launcher buttons look awful now - why did they change this?") then one can discuss whether it's a minor regression or not.
Perhaps launcher buttons couldn't be transparent before and the background setting was a workaround that was made obsolete, just like the absence of an exhaust pipe on a hypothetical car whose predecessor required one. Since the result is almost completely superior, there's little reason to complain about it, but that almost certainly cannot be said for many consequences of these big product upgrades.