I think Trump has delivered on the one thing he brought to the table that middle-ground Trump voters wanted: He wasn't Hillary Clinton.
We have some Trump voters in our office and I've asked them questions similar to this. The basic answer from most of them seems to be that they are still grudgingly satisfied with him. They feel that he hasn't done anything significant, but that he continues to try to plow down the path they want to be followed, he walks their walk and talks their talk, even if he doesn't get legislation passed. Also, most of the people I have asked say they were (and probably still are) more Anti-Hillary than they ever were Pro-Trump. Most of them complain about his "delivery" and his "communication" as being unpolished and undiplomatic and could probably be done better, but they seem to place that at a very low priority in comparison to general positions on things.
I can't speak directly for this perspective because I'm not a Trump voter, but having asked for opinions, I think that is what I'm hearing most often. Hope that helps.