This is basically my whole opinion in a nutshell. I'm entirely against essentialist views of gender/sexuality because they only lend themselves to these stereotypical projections, as you say. Ultimately, (I certainly hope) the fact that I'm gay is not the most interesting/significant part about me and it shouldn't be the same for my characters. Unless it's need-to-know info, my characters' sexual identity is not something I generally I demarcate. *shrugs* Same goes with their race/religion/birthday/favourite Disney film/etc.