Part of what I like about keeping this element of the game complex and multi-faceted is that it allows for really interesting stories to be told with the game that can't get easily told anywhere else. Not that it's something you'll always do, but it's something allowing for this
permits you to do. Once you allow for characters and stories motivated by gender roles in a fantasy world you ennable plots like
Cheery Littlebottom's courage to be openly female in a conservative dwarfish culture where everyone has beards.
Imagine what a warforged thinks of sexual identity - created as a tool for war, they were never meant to have relationships or experience love or have biological urges. What might Sharn or greater Khorvaire think of one that wanted to be a
mother? What if that one wanted to be married to a dwarf woman who the warforged hope to make new warforged with?
Eberron's actually a great setting for this because of its themes of identity - think of what the family life of any Changeling might be like!
In FR, the idea of a cruel gender binary is reinforced with Drizzt's story, where men are not as valuable as women in drow society. Imagine a group of free drow somewhere on FR - imagine one led by the first known male priest of Lolth....perhaps one proud to not be male! Perhaps one ashamed of his maleness, hiding it and attempting to pass as a woman?
Heck, you don't need to dig too deeply into FR to uncover some interesting gender/sexuality plotlines. If the most powerful force in the world is magic and the most powerful source of magic is a
goddess, what happens when a cabal of priestesses start barring men from practicing magic? Hunting them down, robbing them of their powers, claiming that true power is only wielded by women.
The SCAG talks a bit about the lack of gnomish goddesses and how that plays into gnomish concepts of religion and gender and adventure.
A lot of the source material for D&D is riddled with antiquated notions of gender, sexuality, and race. Lovecraft is a notoriously awful racist, and all the greatest pulp adventures were little more than male power fantasies. D&D itself hasn't always been welcoming (Example: read some of the tools in the 2e thief's handbook and realize that it's effectively (a) ignoring the possibility of black characters and (b) actually kind of encouraging painting your face black as a means of stealth). But as we tell our stories today, we have the power as players to change that narrative, to make our Great Old One warlock a black woman who will punch out Cthulu, to make our barbarian kings with scantily-clad maidens draping off of them into barbarian queens with scantily-clad maidens dripping off of them why not.
To me, that's one of the exciting things about an explicitly open welcome to diversity in the game. Like, I appreciate Tolkein's historical position and intentions, but now that Frodo and Sam are characters in my game, I can totally have them snuggling with each other for comfort during the rough times, and yeah, they can say that they're in love with each other (and it can be a doomed romance because Frodo cannot stay in these lands anymore...). Lets see how that changes the story.
Part of the awesomeness of D&D is taking old tropes and making them your own.