I agree that there is not necessarily a phenomenon, because people have been going off the derech as long as there has been that option. It’s not a coincidence that with expanding freedoms came mass “shmad”, e.g. with German emancipation, immigration to America, the rise of communism, etc.
The advantage of seeing it as a phenomenon is when it calls attention to certain problems that cause individuals to go off the derech, such as abuse, poor representations of frumkeit, bad parenting, and other such things.
But it’s a disadvantage when people think that the litmus test in determining whether things are proper is whether they will send people off the derech. It’s wrong to hit people, whether it makes them go OTD or not. It’s wrong to espouse certain extreme views of Yiddishkeit, whether it makes people go OTD or not. Those things are wrong to the people who stay frum and the people who don’t, equally.