Simply enough, I just don't think it's a very nice dress.
I certainly have no issue with feminity (besides the game's tendency to equate it with "make the outfit more revealing") - most of Aurelie's outfits are dresses and skirts, and I love it when I find things that work for my Roegadyn alt.
The Valentione's dress just looks awkward to me. Particularly, the skirt looks incredibly stiff - more like a flat cone than a fabric skirt.
Compare the Thavnairian wool dress (which is actually nowhere near the Valentione's dress in terms of length, but does have a similar construction with stitched ruffles along the lower hem). Look at the texture of it - the small folds and gathers across the fabric. The Valentione's dress doesn't seem to have any of that - just a flat colour, suggesting a very stiff skirt or supporting petticoat. It also makes it look somewhat cartoony.
The patterned tights are going to be hard to find other uses for, at least for me. I'd rather have plain ones.
And I'm just not keen on the top. I don't like the sleeveless look, and it's just... not quite right. I think it reminds me of an apron more than a dress.
Meanwhile, the male version is just nice. It's something you could use in more situations, and it looks stylish.
Personally, I would have liked to get a more feminine version of the waistcoat - more of a blouse maybe, with gathered sleeves, more ornate collar/cuffs and a bow at the neck instead of the tie. Keep the tights, add a nicer skirt (maybe a less-vanishing version of the Quaintrelle's?). I guess the problem would be whether to attach the skirt to the blouse or to the tights - or give two versions of the tights with/without skirt, but then it wouldn't be "fair" that the guys only get one set of pants. But that's another slippery business...
The NieR raids aren't over yet, so we can't say for sure that we don't get a unisex masculine counterpart to the 2B set until we've seen everything that's planned to be released.
On the broader question of whether anyone is actually using the 2B dress or bunny suit... I've seen a few people use it, but more importantly I've seen people wearing pieces of the outfit more often than the whole thing. Would you notice if a male character was just wearing the rabbit ears, or the plain cloth wristbands, or 2B's boots?
In some ways yes, it does mean a disproportionate amount of effort is being put into adapting the core outfits for a small number of people who would wear them, and personally I would love to see more adapted designs instead of transferring the female version straight over, but they're in an awkward position when a lot of people do want the male outfits for their female characters but a lot less want the female outfits for male characters.
Do they take the previous approach of only making the "male" costume unisex while not putting the resources into modelling the counterpart female costume for male characters? (Resource-efficient but leads to people complaining that female characters get more outfits.) Or do they keep the number of outfits balanced with a "both or neither" approach to unisex outfits, regardless of how many people would actually use it?
It also depends what sort of time they are putting into the adaptation work. Are they being assigned it as something to be prepared on a deadline with a planned release date, or is it a background task that they pick up on the occasions when they've finished everything else they had to do (or can currently do) to keep on the current production schedule?
I think you may find there are a small number of people here who repeat their complaint about male-female outfit balance every time it happens, while overlooking things like there being a logical reason to release unisex-male exclusive-female pairs (as discussed above) - and overlooking things like getting new male hairstyles for free while new female hairstyles are locked behind Eureka/HoH.
(Personally, when you have to pay for the outfits I don't see the balance being anywhere near as important as it is for free ones within the game. Though I do find it disappointing that Y'shtola got a new outfit for Shadowbringers - which you know is going to end up on Mog Station - while Thancred and Urianger only got recycled relic gear, which probably won't be sold. That's more of a character-fairness thing as far as I'm concerned, but it's how we end up with the "more female than male NPC outfits on Mog Station" imbalance in the first place, when they put more priority into designing outfits for female NPCs.)
I have definitely seen "male clothing hated" though - there's not enough of it, or it's too feminine when we get it. There was a post a while back complaining that the Adventuring Sweater and Spring Shirt only looked good on female characters (they don't). There were complaints about the Boulevardier set - somewhat justified with dear goodness those ruffled shorts but it's not like you're required to wear the full set, and we already have other pants to combine with the shirt. They're even salvageable if you wear them with long boots so they tuck in, and I've occasionally seen people wearing them as-is - usually Lalafells, but still.
Personally I think we have lots of unisex stuff that looks better on male characters, but that seems to be overlooked in favour of just counting up the numbers of how many unique items each gender gets.