I'm not sure if this is your problem, but my advice may nonetheless help. From your description of briefing cases, I feel that maybe you are getting mired in the details. In the beginning of 1L, I was so obsessed with the facts that I missed the forest for the trees. Eventually I learned that the details didn't matter much and they actually prevented me from applying the ratio to situations that weren't exact replicas of the facts in the case. It sounds scary, but try to distill the facts into as broad of a summary as possible and how the ratio applies to these pertinent facts. Also speak to your professors on how they think the case would apply to other facts. Usually they are happy to elaborate on how this case would apply to other sets of facts (if you're afraid of taking up too much space or appearing like a gunner, do it during office hours).
Also, I agree with everyone else that your colleagues are either delusional about their understanding or boasting (or both). I found there was a lot of bravado signaling in 1L where people alleged to do so little and understand so much. Ignore the noise, everyone has their own process of coping with a new learning environment.