Okay, I can sorta understand why they'd make angels "generic" no-preset-alignment servitors of the gods, and thus you could have evil angels. I mean, we have that in existing mythology (fallen angels, angels of death, etc.).
But archons are no longer the LG protectors of the Mount Celestia (i.e., Heaven) and of innocents, they're the servants of the primordial beings that battled the gods in antiquity. No longer do we have the benign lantern archons, the courageous hound archons, and the noble trumpet archons, we have weird vaguely-humanoid EVIL elemental creatures.
That's ... retarded. It's literally taking 30 years of D&D history (hound and lantern archons appeared in 1977) and saying, "nope, everything we built up about the lore of this creature is wrong, we're changing it, forget it."
Why not create a NEW creature to be the servitors of the primordials? Why radically alter an existing creature with tons of well-thought-out lore? What's next, changing the rust monster to a flying rust-brown fey that likes to heal people in exchange for kisses? Why not make Demogorgon a LG god of peace and bunnies?
Seriously ... retarded.
To those of you involved in the decision to do this to the archons, and other inexplicable changes for the sake of change, I apologize for calling your design choice "retarded." I meant to say "super-retarded."