... whilst Janeway was unable to do the same task with the caretaker.
Janeway was unwilling to even try. She refused to look into the possibility of employing the Caretaker array to send the Voyager on a return trip. If it looked like Janeway were about to lose the array to the Kazon, she always could have destroyed the array at that time.
She wouldn't even attempt an investigation.
Picard would have done more, and with the Enterprise Dee to back him up would have a increased chance of learning the array's secrets. The saucer could have been parked next to the array, while the drive section flew a defensive patrol.
The Enterprise would have had Data and LaForge to examine the array. Janeway had no Chief Engineer at that time, and the head scientist was apparently Ensign Wildman. Janeway couldn't have spared herself for the actual examination, her place was on the bridge.