It’s never too late to become a main warlock 
Well, there have been talks about more diversity in demons, i remember one of the biggest threads to date is from Baal, its a thread active to this day even Warlock Customization: More Grimoires! And other stuff - #1279 by Pepino-frostmourne
And being honest, maybe this kind of threads as constant reminder works, as eventually we got male sayaads; and Demonology have a Pitlord in Dragonflight.
I used to be against those more demons, but, i wouldn’t mind more skins for exiting demons.
Biggest shame about Enslave Demons is that we just don’t see a whole lot of demons in most expansions, if we had, maybe it could be more like MC or Enslave undead(in some SL dungeons) in M+.
Funny you describe that because its basically https://www.wowhead.com/spell=267211/bilescourge-bombers from demonology.