I once had a discussion with R’ Bender about mechanchim. He said the following (probably not word-for-word, but the ideas are right):
“When you were young, most Rabbeim didn’t really know how to be a good mechanech. Why would they? There was no such thing as training to become a Rebbe. Because of the Holocaust, we lost a tremendous amount of our Rabbeim. In the US, most people from that generation were working to support their families. How many people were there who could actually teach children in learning? Most people couldn’t learn by themselves, never mind teach others! Yeshivas had to search for someone when they had an open position, and very often, the people they’d find, while they were talmidei chachomim, didn’t know much about chinuch.
Baruch Hashem, that has changed! There are many more people who know how to learn! We also have classes now to teach people about chinuch, to properly prepare them to become a Rebbe. When a yeshiva has an opening, there are often dozens of applicants, and the yeshiva can choose the best mechanchim to fill its positions!
So the question is, what about the Rabbeim who have been doing it for years? Some of them never had the training, and may not be as “good” as some of the younger, newer, Rabbeim. Yet we must have derech eretz for them, and hakaras hatov for their years of service. They can’t be pushed out!”
Just from my own experiences, I can tell you that many of the Rabbeim I had as a kid were not very good mechanchim. I’ve been through tough times myself, and others have had worse – Feif Un has told me things he went through (and he’s posted some of them here) which are terrible!
But I can tell you that when I went to a yeshiva like Darchei Torah, where R’ Bender carefully chooses every Rebbe, the difference was like night and day. The warmth I felt from every Rebbe there was amazing! I formed relationships I still cherish to today. I am in constant contact with many of my Rabbeim from there. This is the value of a good mechanech.