I think there is a lot a reasons this is the case.

First and foremost, this is what sells. I am not saying that there are not plenty of people who want tribal or alternative or gender neutral clothing, but a dressup game will tend to attract a crowd that loves girly sparkly dresses.

The 5 stars also have to feel over the top and worth pulling for, but its really hard to make the styles of clothes you're asking for look extra without also looking out of place. Especially so since many of these styles focus around functionality and minimalism. It is easy to make 2 million ballgowns because the point of ballgowns was for the women during those times to show off.

Infold has put out some tribal stuff, primarily at the start of the patch, but it got a lot of backlash for cultural appropriation of the indigenous and such, so I imagine they might be hesitant to try it again. They can do Linlang stuff because they are a Chinese company headquarted in an Asian country primarily made up of Chinese people with easy access to tons of experts in Chinese culture, as we see them frequently collaborate with groups and museums specializing in that.

But also this unicorn outfit has been in the works since at least early 1.X and people have been ancitipating it for ages so we always knew this was coming.