You know, this alongside the fact, that Attract still only works on opposite-gendered characters points in the direction that GF is quite reluctant to open up to the " LGBTQ+" community, probably for the parent's sake.
Before I get into the LGBTQ+ customization discussion, I just want to comment on Attract (as well as Captivate, Cute Charm, and anything else that causes Infatuation) only working on opposite gender Pokemon. I have a feeling the idea behind the move is, though they'll never say it, that the Pokemon makes the other Pokemon think it's an ideal breeding partner. It doesn't have anything to do with gender but sex (as in whether you're genetically a male or female), probably effecting the opposing Pokemon's hormones. It's why it doesn't work on genderless Pokemon, they either have no or abnormal reproductive organs/methods thus whatever Attract/Captivate/Cute Charm does won't work.
Remember in Let's Go that they changed the music to classical because they wanted to give parent's peace because they imagined that people wouldn't like techno music.
Wait, really? If true that's going a bit extreme. Like, fine, I can understand not wanting a Rival who's antagonistic, but choosing one music genre over the other because you thought one was going to be "threatening" is getting ridiculous. Don't get me wrong, I like the classical style and I think it is very fitting for the Kanto region. That said, I would also say more mechanical/digital music would be appropriate like when inside a lab. You don't need to go 100% into one music style, infact mixing things up will give areas with different music styles their own atmosphere.
Customization Identity:
To start, I agree with
NormalNavi's conclusion that it's probably due to a technical limitation. The boy and girl models are different so for each to have all clothing/hair styles be compatible they would have to make two versions. Thus they stick to typical gender roles.
That said, it wouldn't hurt for GF to expand on their customization. Because aside from not being able to wear any clothes you want, you can't adjust your character's weight or height. Skin color is limited to 3 tones (there's
at least 6 skin tones if you want to cover a general scale, though
there's scales that have a larger range). Also, maybe include an "ambigious/non-binary" model between the boy and girl models for those who don't fit the typical body molds. I would bring up also letting you change the proportions of your face but let's stick to basics for now. Only thing you couldn't change would be the protagonists age since you're supposed to be a kid... though wouldn't hurt if they let you make an online avatar (even if it only gives you the option to adjust other Trainer Classes to your liking).
But back to clothing and hairstyles. For hairstyles, yeah, I see no problem giving boys a longer hair option to give them that "rocker/chopper rider/hippie" look. Same for giving girls "pixie" cuts. That said I wouldn't quite agree with, say, giving boys the hair style options the girls get to make their hair look frilly. I'm all for free expression, but at the same time I wouldn't want to give the player character options that would take you out of the experience, like having the boy wearing a dress during a serious cutscene (kind of takes the tension out of it if you're distracted by your player's clothing choice). This is where girls have it a bit easier, they can honestly wear boy clothes with no problem (probably why their wardrobe options are bigger, while boys may one a few things only they have the girls usually get what the boys also have plus additional girl options (like boys only has pants and shorts while girls get that plus skirts)).
Really what I think they should do is let you color your clothes anything you want right off the bat. I don't need a dozen of the same style of shirt in different colors, instead just give me one "copy" of the shirt and let me choose what color I want it to be (and let me change it how I see fit). Not realistic? Sure, but I'm not looking for realism here. I'm looking to make my character look good. You can still have different clothing stores all around selling different styles of clothes, but when it comes to color leave that out and when the player puts on the clothes let them choose whatever color they think looks good. You could even make clothes which has two or three areas you can choose the color for (like a striped shirt; choose the color for the base and another color for the stripes). While girls will still always have more options, it wouldn't feel by as much since a lot of that is due to the same style of clothing but just in different colors.
As for accessories like having the boy carry the bag and the girl wear the backpack, sure, why not? Heck, the Gen V and VI boys did carry bags. Now, the boy bags were the rectangular "laptop" bags while the girls got purse-looking bags, but honestly I don't mind that as it gives each gender their own specific style.
(Honestly I could keep going on about customization ideas but this is already on the edge of wishlisting. Let's just say there's a LOT more GF can be doing to make the player character feel more like an avatar of yourself)
Finally, since the Pokemon world is essentially an anime world, how about letting us have our hair and eye color be any color we want. Important NPCs like Gym Leaders and Villain Teams don't have to stick to the natural colors. :P