He's been awful in the sense that you clearly expected a former #1 prospect to be much more dominant at this stage in his career. But I've provided you the numbers. Based on pretty much any calculation of WAR, Moncada is on pace for 1.5-2 WAR season. That is very much an everyday regular and it isn't awful or a trainwreck. You just expected him to be great right away, so being a merely an average everyday regular early in his career is horrible in your eyes.
I don't care to go in circles anymore. I don't think he's been particularly good this year and I am (very) disappointed, but I am also patient. At worst, he's been an average overall player this season. Even if he never improves on his current shortcomings, he'll still have a long career in the big leagues as an average to slightly above average regular.