I am not sure that I would judge church youth groups too harshly. It seems to me that a lot of parents involvement in religious groups is "drop 'em off/pick 'em up".
Recently I was asked to speak about the fundamentals of Judaism to a high school group at a local (very conservative) Southern Baptist church near me. I asked the "youth ministers" (theology students from a local seminary) if the students were biblically literate. The ministers explained that of course the students were biblically literate, this church believes in inerrancy, etc.
So I started the talk by discussing some of Jewish laws/ritual items, and how some of those were reflected in their tradition - in the miracles of Jesus of Nazareth. I started with a Talmudic legends about tsitsit, and mentioned to them that the common translation of tsitsit was "hem", and asked if the hem of a garment played any part in a miracle in their tradition. The kids looked at me blankly. The ministers were red-faced. I talked about Sukkot, when Jews form shake palm fronds and say something that sounds very much like "Hosanna, hosanna, hosanna." I asked if that ran any bells - complete blank looks, Every time I referred to anything from the Christian scriptures, the kids were very lost, until I gave them chapter and verse. The ministers stayed red faced most of the time.
When it was done, one of the minsters told me about the drop 'em off/pick 'em up thing.
I assumed that since the church is one of those places that emphasizes the Bible so much, the kids would know it very well. The reality was that the kids being in a church group didn't mean very much about their beliefs, knowledge, or theology. It really meant that their parents felt comfortable dropping them off there on Sunday night. The parents probably mainly felt that it was a relatively "safe" place for their kids to socialize.
The same may be true of church (and probably synagogue) youth groups in general - it may say something about the parents' social, political, or cultural leanings, and not much about the kids at all.
Mike