Both players fought so hard, both could have won. Wozniacki has improved so much. This is the result, imo, of all the years of working hard to catch up with Serena. Wozniacki's confidence shows that she knows she is now a far better all round player than in the 2010, 2011 years. I reckon that 2018 Woz will easily crush 2010 Woz. Wozniacki today is better, smarter, maybe stronger and fitter than 2010 when she had some fat. Coincidentally, Serena was out during that exact period between 2010/2011 when Wozniacki was winning masters and covering everything but slams. Serena has forced them to be better players and to work harder; Henin, Azarenka, Li, Woz, Kerber etc. It was already clear in 2015, 2016 that yes, Wozniacki had improved, even if she didn't win her slam then. I was already thinking during Tokyo that with her work on her forehand, and bringing the game forward every time she could, meant that she had to win a major eventually, depending on whether she had to play Serena. If there was no Serena to aim for, the 2011 Woz would not have come so far. But Serena also has to be out for a little while to show how much the others have improved. Coincidentally, again, Woz wins her YEC in 2017. But Serena should not out for too long. Don’t forget that Serena was going to enter AO to begin with. Suddenly, after a somewhat dull 2017, they all start playing better. (eg: look at Kerber who completely disappeared during 2017, so completely that everybody nearly forgot her great 2016.) I suppose too that perhaps the prospect of facing Serena in the summer redoubled their endeavour here. Halep must also win her slam too, if she just stays in there.
Surpassing Serena is another matter entirely.