Like everyone has already said here, "Mistake" struck me more with a pop/R&B vibe than anything else. Taylor Swift is definitely country pop more than anything else, though... kind of like Shania Twain, but even more pop-sounding. It's different because Taylor Swift used to have that authentic country sound when she first started back in 2005/2006--or at least, as close as she could get--but started going down the country pop road by around 2011/2012, while Shania Twain was always pretty country pop, with a slight hint of rock.
But I can see why you would think country hit its prime back in the 80s and 90s, because it kind of did, but I definitely think country was at its best during the 60s and 70s when it first started emerging onto the scene. I think country started to change as a whole during the 80s and 90s as pop started getting more and more mainstream success, so country artists probably figured they would do a lot better if they had a bit more of a pop or rock sound. There's still some good country artists left, but a majority of them are definitely country pop more than anything.
I'm not really a country listener and it's actually probably one of my least favorite genres (next to metal), but from what I can tell, 2013 was also a pretty terrible year for country... I hope 2014 will bring better music for all genres, but I honestly doubt country will get anywhere near to what it used to be.