It's definitely combination of new hire and training quality. Some new hire didn't even need to know jepp to pass the interview. They think that "o they will teach me to read jepp" so when it is time to go to sim, they still don't know where to find anything.

When 2-3 people needed extra training, you can argue that they didn't come in prepared or they are slow learners. But when over 90% need extra sim, it may be time to examine the instructors. It doesn't matter how many sessions of cpt or sim you give them if the instructors had all the intention of setting them up to fail!