Using a uniform ranked grading system (i.e. 20% of administrations get an "F"), I don't agree that thoughtful historians can't give the Trump administration an "F".
The list of positives is pretty thin.
Corporate tax rates in line with rest of world is one, but it didn't really result in the hoped for reinvestment or the advertised net bump in revenue.
Middle East accord is something, but wholy threw Palestine under the bus.
Conservatives have to like the judicial appointments, but results in a judiciary that is even further out of line with the majority of the population. Also, credit or blame, depending on perspective mostly goes to McConnell
Pushing back on China trade needed to be done, but lacked coherency, hurt Americans, and was ultimately not effective.
Drawing down foreign troop deployments is inherently sound, but again there didn't seem to be a coherent strategy.
These last two examples of foreign policy (and everything else really) are my fundamental gripe with this administration. There never seemed to be a clearly articulated plan for anything. It was impulsive policy and bumper sticker rhetoric without any real substance all the way down. To the extent that there was substantial legislation it appeared to be driven by McConnell & Ryan taking advantage of a compliant enough president who they otherwise despised.