The utterer doesn't get to determine whether what they say is perceived as a joke by the person at* whom it is spoken. Then waiting for a "nervous laugh" response?
Of course not. What a ridiculous notion. But when one is critical of another's performance and has a stake in that person's performance, it is appropriate to communicate that criticism. And to take the sting out of that criticism, and convey that the matter is a small one but still important enough to call attention to, it is not uncommon to couch that criticism in humor. Of course, it's then the utterer's responsibility to convey the message as such using their choice of words as well as non-verbal language (proxemics, kinesics, paralanguage, haptics, etc.).
If the person
at whom such a criticism is directed responds with a nervous laugh, then you know it was received as intended. If they respond with more concern than that, then you can move to alleviate that concern with additional messaging. If they are oblivious, then maybe you restate your concern more bluntly.
I wonder though if you see my criticism as a meanness because you don't agree with my complaint. Say, instead, that the server insisted on taking your table's order without writing it down (something I see too often) and has gotten your order wrong three times now. It's been sent back twice and now they're back and it's still wrong. Maybe the place is really busy, so you're sympathetic to the young person's situation. Do you just say nothing and pretend it's normal? Some people do just this. They never see it as appropriate to point out the failings of another, even when they are directly impacted by those failings.
Do you chastise him with a formal sounding complaint? I struggle to see how this will do more than add to the servers stress, but at least it acknowledges the elephant in the room ... I guess.
Personally, I might suppose out loud that "Third time's not always a charm." in such a away that my awareness of the busy and hectic nature of the evening's service is evident.
One can advocate for the quality of their service without being a boor about it.