It's more than that, and there is a lot to discuss, but there are a couple of things to consider too.
One it's been, basically 2 days since the finale.
Two, the hook up is pretty unprecedented in american children's animation. Hints, yes, veiled subtext? Sure, but for a MAIN character, in a finale? Shit doesn't happen. So yeah it's big.
Secondly, people like their ships. And I don't mean that as a pejorative, honestly it is the way of shows. Hell, they even got into them when it came to Aang, which always seemed a little odd to me, him being 12 and all, but then again I was so outside the age range of the typical TLA fan that it would be hard to be to look at it that way. Hell I'm not even particularly interested in the ships in Korra probably because the last major ship I cared about in anything was Buffy/Xander, or Angel/Cordy and those haven't been relevant for the greater part of a decade now.
Still, I enjoy stories as they come, and I enjoyed the hell out of both TLA and LOK. I don't post in these parts much mainly because the threads are negative as hell in balance, and that's generally not the discussion that I want to have. Nothing against it, but I think I have LONG gone past the point of hating most stuff, or even bitching loudly about it.
And at the end of the day, the one big thing that MOST people seem to be cheering about right now when it comes to Korra is something I can cheer about too. Korrasami. I mean really look at it, a queer relationship not exactly out in the open, but clearly not in the closet. In a KIDS show. That's huge. I think back to the fact that my father growing up had no gay/bisexual role models in media, and if I have a kid should one of them be queer Korra is leading the way of them having characters that they could identify with is pretty awesome all things considered.