They do not have the resources to work on all three expansions, they already told us this before.
Wotlk still needs plenty of work as many things are bugged. With two populations nearing a combined total of 20k players, its obvious why they are focusing on perfecting that expansion.
Cataclysm is still in a pretty bad state, though I suppose it's gotten better? I don't play it enough to genuinely comment on it.
Mop is ****. Not only is it hard as hell to code due to the significantly more complex phasing/content, it's also missing the most content and has the least open-source code out there. Of course Warmane is going to struggle to fix it. Why do they not open old dungeons/raids? They told us many times before. It's because they aren't scripted, and it seems this is all they will consider on this issue. It seems it doesn't matter that we will one shot the old content anyways, working or not.
The "vote points" we get are meaningless. They are given for just gaining achievement points. They give Warmane absolutely nothing in return. Not sure why anyone would think they keep old content closed for meaningless "vote points". Coins on the other hand, maybe.
Seriously though, given how utterly broken this realm is, how broken PvP and classes are, and how many scripters, let alone abusers (looking at weapon stacking people) are, I'm amazed you Tomsawyer, of all people would care about old content. Does the completely broken PvP not warrant a higher priority to you, as a PvP player? Just curious why you care more about cosmetics and not actual PvP...