Now I'm trying to think of other Disney leads of either sex without a love interest... is there one? Other than those for whom it's not really applicable (ones who are too young, mostly).
Disney even got some flak for "glamming" her up to be like other Disney princesses [1]
[1] https://www.theguardian.com/film/2013/may/16/disney-princess...
There are plenty more. I think it has more been current society that is recognizing it more.
Those are all quite recent, while the historical Disney films all fall into the traditional template of male and female lead falling for each other. To the extent that Enchanted can assume the audience knows the formula that they're parodying.
There is indeed a recognition and a policy change that stories don't have to be made to fit that formula any more. And it seems that the films are exploring other affectionate relationships, such as the sisters in Frozen. Wreck it Ralph clearly has affection between Ralph and Vanellope, but it's more a parental/big-brother-little-sister thing than a romance. Brave focuses on mother/daughter. And so on.
Up (about a guy escaping being sent to an old people's home .. or something).