nail polish on a hangnail

Some superficial or cosmetic change to something so that it seems more attractive, appealing, or successful than it really is. The only thing the new manager has come up with to save the restaurant has been to make a few repairs and slap a fresh coat on the restaurant, but putting a bit of nail polish on a hangnail doesn't fix the hangnail. The new bells and whistles of their latest operating system is just nail polish on a hangnail, if you ask me. It's still just as buggy and unintuitive as the last one they released.

Ugly or useless despite an attractive appearance. This phrase, which is most often heard in “You can put nail polish on a hangnail, but it's still a hangnail,” can be used in all sorts of situations . . . and for all sorts of people.