What would be the correct way to translate into Spanish the idiom: "to miss the point"?
I'm often tempted to write "perder el punto", but it doesn't sound quite right.
For example: "To bring headphones to a concert is like missing the point".
As a native Spanish speaker I really like the English expression to miss the point but unfortunately there's no direct translation. In the context of an argument, you can use:
Eso no viene a cuento / al caso / al tema
Estás desviando la conversación / no cambies el tema
Estás desvariando (warning: sounds harsh)
¿Eso qué tiene que ver? (harsh, too)
In the context of the given example ("To bring headphones to a concert is like missing the point"):
Eso no tiene mucho sentido
Eso es más bien paradójico
¿Es que, para qué vas a ir a un concierto si vas a llevar auriculares? (This rhetorical question is actually the most used idiom - as I said there's no translation for this one.)
I agree with @RomanLittleStork that to truly convey the effect achieved with "what's the point?" one has to go on the offensive.
For your particular example, where you want to critically question someone's judgment in bringing headphones to a concert:
¿Audífonos? ¿Para qué, hombre?
The word "hombre" shows you think the other person is doing something stupid/dumb.
¿Audífonos? ¡Oye, maestro! ¿En serio?
Here, I've used "maestro" (teacher) sarcastically, again, to show I'm questioning the person's judgment.
More generally, I usually use "grano" or "chiste" in situations where, in English, I would use the word "point." Examples:
LLegas al grano, por favor. | Could you get to the point, please?
Note, I've used a strange quasi-imperative here, which is one notch softer than a true imperative, but not as soft as a question (¿Llegas al grano?).
Había un tipo en el concierto anoche que llevó audífonos. Digo, ¿cuál es el chiste de ir a un concierto de rock, si no vas a entrar de lleno en la experiencia, y hacerte un poco de daño a los oídos? | There was a guy at the concert last night who brought headphones. Jeez, what's the point of going to a rock concert, if you're not going to go whole hog, and do a little damage to your hearing?
No guarantees any of the above would work outside Mexico, though.
To tell someone they are missing the point, you would best make an explicit accusation such as :
Oyes, ¡te andas perdido! Which means: "Hey, you are lost!" meaning they are clueless.
In this scenario, in the Mexican Border region, you usually razz them by explicitly aiming the statement at them. Sorta like calling them down on the carpet in front of everyone, so to speak. In the Mexican Border culture, it is customary to make an example of someone's mistake so they don't make the same mistake again.
The word "oyes" means "listen up" or "hear what I say". Oyes is always used to drive a point home. In our culture, we like to "catch" each other off guard and show off in front of others. It is a cultural thing and all done in good fun. It is an integral part of "La Vida Loca".