Regarding Knowledge skills, I think that having lots of them could be useful, but 5e in general suffers (at least thus far) from skills not doing anything specific and instead just being rolled when a somewhat-related situation comes up.
I think this is somewhat by design. The stated goal is that all checks are ability checks, and skills are really supposed to represent specializations in an area that provide a fixed bonus to that check. To that end, I think they're doing a poor job of conveying that idea, but it may also explain the abundance of knowledge skills, to reduce the idea that if you don't have the "swim" skill, you can't swim.
From the previous thread:
Originally Posted by navar100
Reverse metagaming. There are things the characters know that the players don't. Because the players don't know, they don't even know they should be asking if their characters know so they don't even attempt to make a case for knowing something.
In that case, your DM should be providing the information. It's no different than the DM describing the smell of the room, or the dampness of the air. The DM's job is to provide the information to the players that they need to know and should know to make informed choices. Besides, if the players don't know to ask for the knowledge, having a knowledge roll isn't going to help them at all, since they won't know to roll for it.
I don't know if you saw it, but I would be very interested to hear your ideas on my last thoughts in the last thread RE: combat superiority dice.