While I’m sure Mechanchim are to blame in some cases, I think it’s more of a disenchantment felt by children due to issues at home.
Please correct me if Im wrong, but from my observation, the ratio of OTD kids, defined by me as children choosing to be much less observant than their parents, is much higher among those to the right of the YU/Sterns Derech. I think it’s higher among Yeshivish/Litvish/Agudah/Heimish/Chassidish families and lower among those to the left religiously.
In my opinion it’s due to the lifestyle of not focusing on anything but Torah until there arises a serious need for Parnassa, causing many difficult to deal with issues and a skewed value system, where parents are forced to follow the “you gotta do what you gotta do” lifestyle to survive financially, which children are witness to, and Rabbonim in those spheres turn a blind eye to.
In the end, by and large, the homes where the Nachas Ruach is greater, are those homes where there was reality thinking, financial preparedness and responsibility on part of both partners, early on, which is contrary to the teachings of many of our right wing schools.