Tweed
Even if you’re going for a vintage or classical look, tweed is still something that is typically reserved for folks in their 80s. Beyond that, the fabric adds inches to your figure, making you appear heavier.
Cardigans

Another outwear that’s attributed to older men and women. Go for a denim jacket or fitted blazer instead.
Only wearing sensible shoes
While flats are a very handy pair of shoes to keep around, having more shoe options will help. Have some boots, heels, and loafers to mix things up.
“Mom” or “Dad” jeans

We’ve mentioned them briefly, but they should get their own bullet too. These are retro jeans that don’t do any favors. They look like jeans you’ve pulled from the depths of your closet.
Constantly wearing socks and sneakers
Depending on the outfit, these are fine, but if that’s the only thing you got, it’s a big faux-pas with various other outfits.