WARNING: The following contains spoilers for Fruits Basket: The Final Season Episode 13, "See You Again Soon," now streaming on Crunchyroll and Funimation.
The ending of Fruits Basket is a heartwarming happily-ever-after: everyone's doing better after the curse has broken, most of the Sohmas find romantic partners and Tohru and Kyo grow old and have grandchildren together. For the most part, it's extremely satisfying, but there is one big flaw in the anime and manga's conclusions: almost everything ends in the most heteronormative way possible.
Fruits Basket has plenty of bisexual and/or gender non-conforming characters, but with only a couple of arguable exceptions, all of these characters end up in straight-passing relationships and/or start conforming to the traditional roles of their assigned gender at birth.
To be clear, this is not about judging or invalidating the many bisexual people who do end up in straight-passing relationships. This is simply pointing out the trend that, while many Fruits Basket characters have expressed explicit or implicit attraction to people of multiple genders, every single canon endgame pairing in the show is between a man and a woman. Hatsuharu's first love was Yuki, but he ends up with Rin. Any potential chemistry between Yuki and Kakeru was ultimately abandoned once the Yuki/Machi romance started developing. Even Hana, who had no explicit romantic subplots and was very easy to read as sapphic, is ultimately paired up with a man according to the Fruits Basket Another sequel manga.
That all these explicit or implicit homoromantic subplots came and went while the characters were in high school lines up with general trends in anime and manga to treat high school as a time where teenagers are free to experiment before ultimately ending up in heteronormative relationships. The one major exception to this trend is Ayame. While he also ends up with a woman, he still proudly expresses his attraction to all genders as an adult, making him feel more like genuine bi representation rather than treating bisexuality as a phase. Ayame is also the only one of Fruit Basket's four significant gender non-conforming characters to keep his androgynous presentation consistent throughout the series.
The other potential bright spot for queer inclusivity in the series finale is when Momiji notes that he's looking for a "significant other" without specifying any gender. While Fruits Basket Another confirms that Momiji ultimately married a woman, at least as far as the anime is concerned, this line opens up the possibility that Momiji might still be willing to explore his sexuality after high school and not as a "phase." Momiji's gender presentation has become more masculine since his growth spurt, but this was built up naturally (his plan was always to crossdress as a kid and wear men's clothes as an adult), and his expression of masculinity still makes plenty of room for softness and cuteness.
As for the other two formerly gender non-conforming Sohmas, it's a positive thing that Akito is finally able to express her femininity after being forced into a masculine presentation by her family for so long. Ritsu's ending, however, is what pushes Fruits Basket too far towards cis-hetero gender-normativity. One of Ritsu's big defining traits was that crossdressing was one of the few things that calmed his extreme anxiety. Ritsu cutting his hair and giving all of his womens' kimonos to Kagura in the finale might have been meant to say he doesn't need this coping strategy anymore, but Ritsu's arc is so poorly developed over his minimal screentime that this doesn't come across strongly. In combination with the other stories, it plays as the most problematic example of Fruits Basket treating gender conformity as akin to growth.
In a way, the very premise of Fruits Basket is going to prize heteronormative relationships above all others: the curse prevented the afflicted from hugging the opposite sex, so inevitably opposite-sex attractions were going to be the biggest source of drama. However, there still could have been plenty of drama to be found with a more explicitly queer Sohma storyline. Momiji's issues with his mother and sister, for instance, made for some of the most affecting drama in the series without being tied to romance at all, so there's no reason we couldn't have had a Sohma with a committed same-sex partner struggling with similar curse-related issues. It's important to remember that the Fruits Basket manga is ultimately a product of its time, and the recently-concluded anime faithfully adapted the source material without really modernizing it.
All episodes of Fruits Basket are now available to stream subtitled on Crunchyroll and dubbed on Funimation.