True, but does this instantly mean that fairy as a whole is an "unbalanced" type? The two types it's weak to may not be extremely common in offense, the moves, and mons that are commons completely send fairy into the ground, in this sense they both got a buff. Now let's take a good look at the two types that had been completely unbalanced in the past: psychic and dragon. Psychic, while only for one gen, only had one real weakness. and the only move that type could bring out to even scare them was Pin Missile. This led to it being nerfed in gen 2 with dark being introduced and ghost now hitting it (granted ghost was still physical and physical ghosts were not a thing until gen 3). Now we look at dragons, a type that has had only 2 weaknesses for 5 generations. those being Dragon and Ice. Ice is a common type of offense, but the second you look at the resists you can understand how Dragons didn't always mind seeing an Ice type. I mean for crying out loud most of them can learn fire or rock type moves (not always reliable, but reliable enough to warrant the ice weakness checked), and the dragon weakness came down to "Which Garchomp is scarfed/which chomp wins the speed tie. And then we look at fairy. And instead of seeing Fairy having only steel and poison as a weakness as fairy being "unbalanced" or "Broken", see it as a Buff for poison and steel (and to an extend fire). Two types that for offense were about as bad as Ice was for defense. And if Fairy was only strong against Dragons people would have complained because "It's was made to kill dragons and nothing more, pretty shit move.". The reason Dark, aka Evil in Japanese, might have become weak to it could be that in pop-culture fairies are usually shown as friendly and helpful pixies. for fighting... I guess they learned from poison and steel and thought 2 types to bust were too little and slapped fighting there? IDK. Maybe it resembles Magic over Brawn?
In any case. My point was, and still is (yet it seems some people either just ignore what I try to say on the subject or are a bit too stubborn to try a fairy team out and see the weaknesses and the balance of the type), that fairies are nowhere near unbalanced. Gamefreak didn't add them without running some tests about it (I assume) and assuming they learned from Dragon and gen 1 psychic I don't think they would instantly break the new type. This does, however, not speak for the individual mons Fairy has at its disposal. I mean looking at just the tapu's magearna and Mega Diancie it seems really broken, but how many OP dragon legends have we had? Looking at the type as a whole will show that even with the broken ones (Tapu Lele for example) Fairy is still a completely balanced type. I will now have to mention @Hycrox, as he has never truly dubbed fairy to be Unbalanced, but simply dislikes the type because it has a lot of annoying mons (I think he didn't even mention the mon that helped ban Swagger, so I guess Klefki isn't that annoying?).
Each reason for disliking a type is valid and I will not deny that. But before you call a type unbalanced, look at it from both sides. There are more MU's that fairies dislike that most of the people dubbing it unbalanced would even think. a nice example is Fairy Ground. On the surface a balanced battle with Fairy having the upper hand because of Tapu Bulu and Azu. and while this to an extent true, it also isn't. Ground has ways to block azu and the two Nido's that can OHKO every tapu bulu. Tapu Koko can only really use D-gleam and HP Ice, Klefki cannot set up screens reliable and need I even mention Exca? And before you say "But fairy has ways to deal with the checks", yes, they do. but this is a Hypothetical battle. and in that Ground can curb stomp fairy easier than many believe (the reason I used ground btw is that I spoke on normal v fairy enough times and I think you all know which type has the upper hand in that battle)