I've always been surprised at Moniak's lack of walks. He was a patient hitter in high school and on the circuit with the other high-level players at that age. It would be great if he could increase his walk percentage to at least 7.5% or 8% of his ABs (note he moved up from 5% to 6.5% last season). That would push his OBP into the useful range. I don't know if he's swinging out-of-zone on breaking balls or chasing too many close pitches overall, but I'm sure the coaches have an idea what's up.
Interestingly, Josh Stephen (admittedly a personal favorite going back to his GCL days) had an awesome year that would have made us crazy Moniak fans if he had posted it. He was 40% above league average offensively according to wRC+, which is park adjusted. Moniak was only 15% above league average. The biggest difference between the two is walks, where Stephen was at 10% of ABs. Also, Stephen is primarily a LF now, where Moniak is still mainly in CF. Finally, Moniak had a much larger home/road split than Stephen, but Stephen was very bad vs. lefties, whereas Moniak was pretty even vs righties and lefties.
Teach Stephen to hit better vs. lefties, and Moniak to have an actual platoon advantage and you have two pretty good OF prospects.
(Note-Stephen had a 940 OPS post-all-star break. Either he really adjusted to the league or he had a prolonged lucky hot streak. Moniak, as usual, tailed off at the end of the year, posting his best month in June.)