You are forgetting about Steel type's buffs, namely its resistance to Fairy moves and Steel moves hitting for super effective against Fairy-types. This means that Skarmory will at least be a check to any physical Fairy-type that manages to become OU, and as FrostFire mentioned, Skarmory couldn't handle the Ghosts of OU anyway while CB Tyranitar's Crunch doesn't 2HKO Skarmory (Stone Edge is the real problem for Skarmory).
Scizor also may have lost its ability to switch into Gengar but now it can easily revenge kill Fairy-types.
The buffs that Steel-types received easily outweight the nerfs imo.
Honestly, I'm not so sure about this. The buffs are entirely dependant on an unknown quantity (the quality of fairies), while the nerfs are very much known and very much negative. Personally, I think people have been really overhyping fairy types, and thus that the resistance and super effective hit Steel gained will not be nearly as useful as the Ghost and Dark resist.
Either way though, everything lies in how good fairies are. Personally, I look at the typing and think it is rather mediocre. Defensively the resistances are pretty nice, but small in quantity. I think it will make a great secondary type defensively, but by itself, its not really all that great, and paired with something bland defensively (like say Wigglytuff with its Normal/Fairy), it will really not be all that good. If paired with a better defensive typing, it could be great, but by itself, its nothing special. Offensively, Fairy is underwhelming. SE on Dragon is cool, but outside of obligatory STAB moves, it is fairly useless as a coverage option as Ice does it better. SE on Fighting is nice too, but again, this is more useful as a STAB thing. Fighting types are not something you usually need coverage for as they are not exactly the wall type. Powerful neutral hits are more useful than spending a move on fairy coverage for them. And finally SE on Dark, which is nice, I guess, but nothing special. Dark is not the most common typing, so while its a nice thing to have, its not anything worth writing home about. And, of course, being resisted by Steel and Fire does it no favors. Overall, I just don't see Fairy being a super offensive typing. Rather, I see it more like Flying this gen. Nice to have as a STAB, and a niche coverage option for a few guys, but in general, just there, providing some passive defensive benefits to dual types. It certainly won't be an offensive powerhouse like gen 5 Dragon or Fighting.
And with that said, I just don't think that Fairy will be all that dominating. And if it is not that dominating, then the buffs to steel are not that great. And so I really do think Steel did not get better by its presence. I won't say it necessarily got worse, but I see it more as a neutral trade that Scizor and other offensive Steels appreciate more than the defensive ones.