Você sabe o que off the rack significa?

Since Friends is one of the sitcoms I watch the most [even having its last episode shot a lot of years ago], that's where i get most of my expressions from. This time, I was watching the episode 7 from the second season and here's the situation: bride-to-be Monica is in the middle of a meltdown after finding out her parents had spent all the money for her wedding. A wedding party seems to be one of her greatest priorities at the moment and now her friends are trying to calm her down by saying things like "it will be fine", "you don't have to have this rustic Italian feast". Among the many things they said as an attempt to make her calm, one of them caught my attention. Rachel said: You can still wear off the rack. Do you have any idea of what that means? When you wear off the rack, or wear off-the rack clothes, you wear clothes that are marketed in a finished condition in standard sizes, clothes you literally take off from racks at a store. If you don't know what racks are, they're those objects you use to hang your clothes on. Stores use them to stack in their clothes so they'll be more organized and easier to find. So now you understand Monica's dilemma? She would have to wear a ready-made wedding dress that anyone else could get, not an exclusive dress made to her size and style. Rachel said it would not be a big deal to wear off the rack, but she didn't mean it. She also thought that was like reaching rock bottom. But what do you think? Do you see any problem in wearing off-the rack clothes?