Even though I don't like making long posts on the forums, I'm going to make an effort and write something about Hoopa-Unbound. I'm not going to stay silent with all these false accusations going around.
Let's start from the beginning, suspecting Hoopa-Unbound was a mistake in my opinion. I do not see how it contributes to our dull state at this moment, when all we see around us is the same types repeating themselves. Taking a look at its movepool, we may see how versatile and unpredictable Hoopa-Unbound can be, but if you look closely at the metagame you will understand that it's not that mysterious. We shouldn't compare our pokemon's roles to OU ones and how it fare their and insert it here. Hoopa-Unbound carries with it known moves, Hyperspace fury, Hyperspace hole/Psychic, Energyball, Gunk shot (On dark), Drain Punch (On psychic) and Fire Punch from time-to-time. I might sound dumb to you, but that's all what my eyes have witnessed. Hyperspace fury is the obligatory STAB move alongside with Hole which makes Hoopa-U a strong mixed user. Drain Punch helps Psychic taking on Steel-types that are hard to deal and Eneryball helps against the omnipresent Water-types, on the other hand Gunk shot is preferred on dark due to it's capability of taking out Fairies, but I fail to see the unpredictability that Hoopa-Unbound gives and why is everyone afraid of it.
I'm going to try and understand your point of view and see Hoopa-Unbound being versatile and broken on Psychic. Yes, it can run many items (Scarf, Life Orb...) and helps psychic taking on their common weakness such as Steel-types. Yes, it can run a specially offensive set and abuses of its mixed appearance to bluff the opponent but don't tell me that it can't be checked by every type. Okay, from your point of view types such as Rock, Ghost, Psychic do cripples under the presence of Hoopa-Unbound, but isn't that the case of Mega Sableye vs Electric, Poison, Ghost? or Ghost, Psychic, Rock and Ground vs Mega Gyarados? or Fire, Dark against Mega Diancie? Please enlighten me more.
Also, heading toward Psychic do you really think it's going to use too much if Hoopa-Unbound is banned? Do you really think that will stop Psychic overpowering other types thanks to plethora viable psychic types that deals a lot of damage to other types such as Mega Gallade, Mega Medicham, Slowbro, Mega Gardevoir, Mew. I'm not saying they are broken OR ANYWHERE NEAR HOOPA-UNBOUND but I'm giving a bird view of Psychic's power that will not change even if we ban Hoopa-Unbound.
On the other hand, Dark which already has a limited amount of choices to take on their weakness unlike Psychic will suffer more in the hands of ORAS which was already cruel to it. I'm not going to talk too much about dark since everyone will etiquette me with the word ''Biased'' but I'm going to share an opinion about it. Even with the help of Hoopa-Unbound dark falls prey between the hands of common types such as Water-, Flying-, Fairy-, Fighting- types and to an extent Psychic- types and to Pokemon such as Manaphy, Mega Venusaur and will lack a viable scarf user. I have used Honchkrow for the purpose of compensating the cruelty of the matagame, it is effective but it isn't as powerful as Hoopa-U, and it doesn't provide enough coverage, bulk to accomplish its job. Against fighting it takes damage from recoil more than it deals, it isn't as strong to deal with Water- types and accomplish nothing against flying. I won't repeat what
EienSeiryuu said, go to his post and read what would happen if Hoopa-Unbound gets banned in dark.
This said, Hoopa-Unbound as strong as it doesn't create holes in the metagame as everyone pretends it does, it may seem unpredictable but in all seriousness it's not with the games I have witnessed. And the question that asks itself over and over again, are we really going to sacrifice a balanced metagame that is a little bit scratched to make dark suffer more? Are we really willing to ban something that cripples a type without even scratching the other type? Are we really willing to create more unbalance? Decision is in the community's hands, don't make the bad move again.
In this second part of the post, I'd like to derail a little bit and dive deeper in the type-ban only decision. What was the reason that made us make this decision? In most cases, we are seeing that a Pokemon is deemed broken in a type but banning it hurts the type that it's not broken in it taking for example, Hoopa-Unbound and Mega Sableye. I remember we did that policy because new users will find difficulties integrating the metagame, but was is it a sage decision? We're an OM and not a tier, so complex bans must be issued to makes the metagame balanced specially in Monotype, a restricted field. Also is it fun for a newcomer to play Monotype and see the same type over and over again just for the sole reason that X Pokemon is broken in Type B but Type Z needs it so badly that it becomes one of the worst types without it. Why is Aegislash allowed such privilege but not Hoopa-Unbound or Mega Sableye. I think it's time to review that policy because the metagame has become dull, and people doesn't like seeing the same types repeating themselves on ladder. I'm ready for the hate tbh, but that's what I needed to get off my chest because I completely disagree with the suspect.