well to me it’s art, it just depends on what you’re looking at. like fashion, there’s art to be viewed and art to be bought, so basically aristocratic art vs commercial art- couture fashion vs rtw fashion.
i suppose while rtw fashion is more for the masses to be bought, the art that you find in fashion deals with the ability for designers to create pieces that are to be viewed for the purpose of beauty- pieces that take up to 300 hours of handy work by over 100 seamstresses etc in a house to create one dress… yeah that is definitely art. (i.e dior, chanel, mcqueen)
you can look at it from a business pov too if you’re not into the creative aspect of fashion, whenever a designer makes something for couture, it’s usually a massive loss for the house. so much time and effort taken to make a piece that usually doesn’t get sold because it’s not wearable (sometimes some pieces are too much for even red carpet events, so it ends up being archived or put on display at museums for a set amount of time). look beyond that and you get photographers. the world of fashion has enabled any person with a camera to be able to capture someone wearing something amazing and that’s considered a form of art- street-fashion-art.
so, yeah fashion is pretty much art, but it’s more of a cultural movement of art (or trends). i think it ranks up pretty well in the world of painting, sculpturing and performing arts.