Okay, but I doubt many children were begging their parents to take them to Brave because Merida might not be straight, and because they were longing for a subversion of Disney's traditional heteronormative expectations.
Well, of course. The whole point of subversion is that it's sneaky, that it's not what you expect going in. If it were blatantly advertised up front, it wouldn't be effective as a subversive message. The
sub- part means "under," after all -- as in slipped in under the radar. To subvert is to undermine, to dig in below something in order to weaken it.
Brave superficially
looked like just another Disney princess movie, but its meaning was in the way it overturned those expectations. Merida was being pushed into the conventional Disney-princess mode of finding her Prince Charming and marrying him and living happily ever after, and she defied that and tore down the whole assumption that a woman needs a husband in order to be fulfilled.
I mean, even the more recent, empowered Disney princesses you're trying to compare her to end up with their true loves at the end (at least the ones I'm familiar with). I love Rapunzel's independence, for instance, but she still ends up marrying Flynn, and the story is about her seeking the freedom to
find true love. Merida goes through the whole movie without encountering a single male character who's remotely worthy of her affections, and she ends the movie happily single. The real love story in the movie, the story of two people finding each other and building a lasting, fulfilling relationship, is between Merida and her mother.
(It may be that
Frozen defies the pattern as well; I may be the one person who hasn't seen it, but I gather it's more about the relationship between two sisters than about romance, though there is a romantic subplot. But
Brave came before it.)