Craigslist became popular when that was the clean look for a website, and then never bothered updating. Network effects in action.

Temu offers people the ability to save money. If your product is "X, but cheaper" you can have a worse UI than X.

Sometimes utility can be so good, users don’t care about design. I was also thinking of it as a business coming to a SaaS website. B2C is filled with so many dark patterns, first impression probably plays less of a role.