Anecdotal evidence. I had not even seen that thread, and I bet most people don’t even visit the forums that often. However, perhaps there is some truth to it.
We RTS gamers have become a niche, and the subgroup that only wants campaigns and doesn’t care that much about multiplayer like you and me, we are probably even worse in a niche of a niche situation. Yet, even so, even if Blizzard doesn’t bother making campaign maps anymore, they should at least make sure their game engine doesn’t fail when it comes to supporting community made ones in that regard.
Hell, Blizzard could at least make sure basic things work!