hi, can someone explain me what does 'must be nice' means? I understand it as a phrase but I don't get the context in ripndip's clothing. I would say that they're a bit specific (idk how to describe it) but I don't know story behind these words or any context. maybe it's popular phrase to use?

See a translation

'Must be nice' does sometimes mean that the speaker can't personally relate but thinks it sounds nice.

But USE THIS PHRASE WITH CAUTION. It has a moderately negative connotation. It is often a "passive-aggressive" comment. The meaning is that the speaker thinks the receiver is bragging, unrelatable, or insensitive about their joy, and the speaker is jealous.

Example:

Annie: "How did you do on the exam?"
Brittany: "Not good. I studied all day, and I only got a C."
Annie: "Oh, really? I only studied for an hour, and I got an A."
Brittany: "Must be nice..."