I'm old, so there are lots of things that younger folks do and like that, I find kinda "funny" but when I was younger, I did stuff that perplexed or aggravated my elders too!
My approach is multifaceted. In some cases, I feel if you can't fight 'em, join 'em. Some of the newfangled stuff is fun! OR, If whatever it is, is not harmful or infringing on my life, I'll "just get used to it"! As THEY say, it is waht it is!
So here's MY gripe list: As an audiophile and a lover of great music, rap music over the horrible PA system and dreadful acoustics in the supermarket is nerve-wracking! Nothing can be done- they can't change the "radio station" it is all streamed from "somewhere" and all the local stores subscribe to the same service! Then, when the younger folks make announcements they shriek into the phone or mic, not realizing their voice is gonna be amplified. "The garbage compactor at the rear of the store is now open" is just what I need to hear when I am selecting my overpriced organic vegetables!
Tattoos on the face and face piercing give me the willies- but it ain't my face and body. They'll be sorry when they get older. How about those massive holes and grommets in the earlobes! Well, it's none of my business until they come into my studio for a portrait sitting- with their grandmother!
Devices and phones at the dinner table, texting while driving and walking into traffic- UGH! Nothing wrong with social media unless you live your enter life online!
Selfies are fun and harmless. Y'all amateur psychologists like to tag folks with funny habits as having serious mental, behavioral or psychological disorders- that's not nice. I guess we all do it and bandy about terms like paranoia, multiple personality (schizoid) tendencies and narcissism, etc. Those can be devastating illness not merely annoying habits!
"Selfie" is just a relatively new buzzword- as others have alluded to, self-timer, long pneumatic, and remote controls have been around forever. Funny, I had all the self-timers in those MXV shutters disabled so the timer did not accidentally kick in when I was trying to grab an important shot.
The only thing I find disturbing on my cell phone camera is when the "selfie" mode kicks in unexpectedly when I am trying to shoot something and my face appears on the screen. Some mornings it's enough to stop an 8-day clock and make it run backward-UGLY