"Although we are not under the Mosaic Law, its requirements give us insight into
what is acceptable or unacceptable in God’s sight."
(I never was a JW).
This quote is an excellent example of the problem that christians have in trying to maintain continuity from the OT god, bridge the gap between the god of vengeance and 'gentle Jesus, meek and mild'. (Especially the xians who relegate the books of the Maccabees, etc., to apocryphal status). It was a problem for me when I was, a long time ago, a BAC. The doctrine of a .'new covenant of grace' and the other explanations don't really cut it and don't square with the unchanging god teachings. There's a good reason, I think, why most don't like to ponder these points (they're in the 'too hard' box) and it's a really difficult point for JWs because (it seems to me) WTBTS is much keener on OT than NT. (Is it coincidence that Beth Sarim was designated for use by the OT 'princes'? - after Rutherford was finished with it, of course).
The logical problem is quite straightforward. A law is either in force or it is not. If a law is no longer in force it is because it has been repealed, and laws are repealed or superceded because they are no longer applicable or relevant or in accordance with current views. Their insights into what was acceptable is discarded. (Easy examples are laws concerning slavery, homosexuality, etc.)
Probably the most widely-known item under mosaic law is the prohibition of eating pork. Simple to understand, not much interpretation required. No great scholarship required to decipher the 'insight' into 'what is acceptable'. And yet, AFAIK, the GB, that almost-but-not-quite-divinely-inspired distributor of god's instructions, has rarely or ever issued a pronouncement on this vital subject.
One could make the point that a god who was at least as competent as an average legislator could make his laws at least as clear-cut as man-made laws (which is to say always open to interpretation on the finer points) and not rely on vague 'insights'.
Here's a topical example from the UK. The age of consent is 16, Until the 2003 Act, a teacher who had sex with a 17 or 18 year old pupil committed no criminal offence. Since that Act, a 'person in authority' who has sex with a person under 18 commits a crime. Straightforward, no 'insight' required.
Although, in my example it's not clear what the situation would be if the pupil was his/her wife (age for marriage is 16). Forget that.
My point is - by this quote the GB is strengthening their position that THEY are the ones who can interpret the insight into what is 'acceptable'. This is rubbish.
(PS - apologies for rambling.)