I think your justifications of how the system currently works is a justification for why the encouragement, invitation, and inclusion of a more diverse audience is important for the future of fantasy.
This is not about the expressed interest of the reader or gamer being attracted to a certain genre, because there is abundant evidence to show the limits of many of these creator's imaginations only go so far, so far to include fantastical magic, monsters, and epic battles, but not far enough to consider real people different from the creator's field of experience who might populate these worlds. Because how those real people are represented is what will communicate to the outside world who these fantasy worlds were explicitly created for.
No matter the setting, realer representation of real people is what makes fantasy believable.
We can examine fantasy and be critical of its flaws while still enjoying it--this is not about every fantasy passing a certain criteria to be acceptable--but we can stop and recognize the shortcomings of what we're building upon, and realize how that can cripple the future of fantasy.
I love reading Tolkien. But the more I want to find out about Middle Earth, the more I see that it's like the real world, unfortunately. There are histories we won't ever know about because the author of this fantasy world simply did not consider certain things.
We won't know more about Dwarven women other than a footnote at best. The works of Tolkien, like so much of the other foundations of fantasy, are considered sacred, and archetype.
If the real world influences fantasy, then the reverse is also true. Our collective myths, stories, art, films and games have influenced how we see the world. Taking an active role in positively shaping the future of fantasy can positively shape the real world.
I don't think it's fair to put the responsibility for being included in a genre solely on the groups who wish to be included--there is responsibility on the current creators of fantasy to realize they are setting an example, because they are the examples we look to when citing representation.
More people than ever are enjoying fantasy and board games for the first time. It would be hypocritical for anyone who calls themselves a nerd, geek, or whatever to not be inclusive of someone else who is also different from enjoying fantasy too.
Back to the business and marketing argument, check out this snippet from D&D version 5 character creation basic rules:
The elf god Corellon Larethian is often seen as androgynous or hermaphroditic, for example, and some elves in the multiverse are made in Corellon's image. You could also play a female character who presents herself as a man, a man who feels trapped in a female body, or a bearded female dwarf who hates being mistaken for a male. Likewise, your character's sexual orientation is for you to decide.
Including this takes nothing away from players who already enjoy the game, but adds so much for players who are not traditionally considered "the target market." Marketing is about dividing people up in easily analyzable subsets so they can be served advertisements more effectively--to say that it's a real representation of how people function is giving them too much credit.
Rather than digging your heels in and defending tradition, consider the positives that fantasy has given you over the years, and try to imagine if you were never you, you were someone else, a kind of person not represented in fantasy, because, for no good reason, a person like you being gainfully included in a fantasy world is more unbelievable than a fire-breathing dragon.
Fantasy for all.