People on the internet tend to be binary. it is possible to think the season was a success and think the GM and manager are extremely promising and still be deeply disappointed with how they executed certain things, and some of their decisions.
But, no matter what kind of brass you have, their impact on the field is greatly overstated. Players play. If a few more of them had lived up to or exceeded their potential more consistently they'd still be in the thick of it And if they'd done so less consistently we wouldn't have anything to be disappointed by. The management gets credit for both of those things but not that much, really.
And I think Klentak and Kapler's mission was to experiment and develop while waiting to go big in the 2019 off-season. It if it had really been to go for it in a weak NL East we would have seen more dramatic moves at the deadline (and we know what they could have been). If Middleton wanted them to change course presumably they would have done that; it's unlikely they aren't on the same page, or that he's dissatisfied with anybody's job performance except in a normal, evaluative, what do we do next year kind of way.