Choosing not to pick a covenant of your choice just due to the cosmetics is a dumb reason… What are you expecting? the necrolords to have fairies, flowers, butterflies and rainbows too?
or the venthyr to have Angels and such flying through the skies instead of bats and gargoyles?
This is no different than Legion where you as a rogue were confined to the sewers. while other classes got to be in class fantasy areas everything from nature to grand temples to demonic realms.
Fantasy and Immersion > player cosmetic/transmog preferences.
Really no point of playing a MMORPG if you expect blizzard to make every single zone or area or cosmetics a cookie cutter duplicate of every other zone or area… you may as well play a mobile game for that type of cookie cutter gameplay.